Overview of the Symplectin Gene (sympp) in *Sthenoteuthis oualaniensis* (Purpleback Flying Squid) OpenAI o3-deep-research-2025-06-26 99 citations 2026-05-02T16:47:58.752967

Overview of the Symplectin Gene (sympp) in Sthenoteuthis oualaniensis (Purpleback Flying Squid)

Symplectin (gene sympp) is a photoprotein luciferase uniquely found in the purpleback flying squid (Sthenoteuthis oualaniensis, formerly Symplectoteuthis oualaniensis). This enzyme underlies the squid’s bioluminescence by catalyzing a light-producing reaction using the marine luciferin coelenterazine (pmc.ncbi.nlm.nih.gov). Unlike more common luciferases, symplectin is categorized as a photoprotein because it forms a stable complex with its luciferin (coelenterazine) until a specific stimulus triggers light emission. The squid’s dorsal photogenic organ contains symplectin and emits an intense blue flash (~470 nm) when stimulated (pmc.ncbi.nlm.nih.gov). This flash mechanism is an evolutionarily specialized trait of S. oualaniensis, making symplectin a unique enzyme adapted from a widespread metabolic protein family (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

Structural Features and Family Classification

Protein Family: Symplectin belongs to the carbon–nitrogen hydrolase superfamily (pmc.ncbi.nlm.nih.gov). Sequence analysis revealed ~30% identity to human vanin-1 (pantetheinase) and ~31% identity to biotinidase (pmc.ncbi.nlm.nih.gov) – both are amide bond hydrolases that typically act in vitamin metabolism without requiring cofactors. Like other family members, symplectin presumably contains the characteristic catalytic triad (a glutamate, lysine, and cysteine) in its active site (pmc.ncbi.nlm.nih.gov). Indeed, comparative modeling based on human vanin-1 suggests symplectin shares a two-domain architecture: a “nitrilase” catalytic domain and a secondary “base” domain (pmc.ncbi.nlm.nih.gov). Vanin-1 is known to function as a dimer, and structural modeling indicates symplectin may also form a head-to-tail homodimer, where the active site of one subunit could interact with the luciferin bound on the other subunit (pmc.ncbi.nlm.nih.gov). This dimeric arrangement might be important for its bioluminescent mechanism, as discussed below.

Domains and Post-Translational Features: Consistent with its homology to vanin/pantetheinase proteins, symplectin contains conserved regions identified as Biotinidase/Vanin domains (Pfam CN_hydrolase, etc.). The UniProt entry (Acc. C6KYS2) notes motifs such as C-N hydrolase (PF00795) and Vanin_C domain, which are hallmarks of this enzyme family. Family members like vanin-1 are synthesized with a signal peptide and are GPI-anchored to membranes; by analogy, symplectin is likely produced as a preproprotein with an N-terminal signal sequence for secretion and a C-terminal site for GPI anchoring to the membrane. In fact, the originally reported symplectin cDNA was incomplete at the N-terminus (missing the start methionine and ~30 residues) (pmc.ncbi.nlm.nih.gov), suggesting the missing segment could include the signal peptide. Experimentally, the symplectin holoprotein runs at ~60 kDa on SDS-PAGE (pubmed.ncbi.nlm.nih.gov), consistent with a polypeptide of roughly 520–530 amino acids (including any signal sequence and propeptides). Importantly, the enzyme retains cysteine residues critical for structure and function: for example, symplectin has several conserved disulfide-forming cysteines and one free cysteine (Cys-390) that plays a special role in binding the luciferin (discussed below) (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

Biochemical Function and Enzymatic Mechanism

Luciferin Binding and Photoprotein Mechanism: Symplectin’s primary function is to catalyze a bioluminescent reaction. The squid uses the widespread luciferin coelenterazine as the light-emitting substrate. In S. oualaniensis, coelenterazine is present in a stabilized form known as dehydrocoelenterazine (DCZ), which is stored covalently bound within symplectin (pmc.ncbi.nlm.nih.gov). Specifically, a molecule of DCZ attaches to the enzyme’s Cys-390 side chain via a thioether bond (pmc.ncbi.nlm.nih.gov). This covalent chromophore attachment defines symplectin as a photoprotein: the enzyme-chromophore complex remains in a resting (apoenzyme-bound) state until a trigger causes the reaction to proceed.

Light-Emitting Reaction: Upon stimulation, symplectin catalyzes the oxidation of the bound coelenterazine, resulting in an excited-state product that emits blue light (peak ≈470 nm) (pmc.ncbi.nlm.nih.gov). The chemical reaction is accompanied by the decarboxylation of coelenterazine – mass spectrometry of a synthetic analog showed the loss of a CO₂ (roughly 12 Da), confirming that light emission involves breaking a carbon–carbon bond and release of CO₂ (pmc.ncbi.nlm.nih.gov). The overall reaction converts the coelenterazine derivative to an oxidized coelenteramide (or similar product) while releasing a photon. This matches the chemistry observed in other coelenterazine-based luminescence systems, though symplectin’s mechanism is unique in covalently pre-binding its substrate.

Notably, molecular oxygen is required for the light-producing reaction (pmc.ncbi.nlm.nih.gov), indicating that symplectin likely uses O₂ to oxidize the luciferin (as is typical for luciferase reactions). The enzyme’s catalytic cycle can be summarized in two phases: (1) a charging phase where apo-symplectin binds and stabilizes coelenterazine (forming a peroxy-coelenterazine intermediate, perhaps similar to other photoproteins), and (2) a light-emission phase triggered by specific stimuli, yielding a flash of light and leaving the enzyme in an oxidized, “discharged” state. After a flash, the spent chromophore (now coelenteramide or a derivative) must be removed and replaced by fresh coelenterazine to restore activity (pmc.ncbi.nlm.nih.gov). In laboratory studies, researchers achieved reconstitution of symplectin by providing exogenous luciferin analogs: for example, adding ortho-fluoro-dehydrocoelenterazine (F-DCZ) to the purified apo-protein recharges it, and the complex can then emit light upon stimulation (pmc.ncbi.nlm.nih.gov).

Reaction Kinetics: The bioluminescence produced by symplectin is characteristically a rapid flash. Early research described an “intense blue flash of light followed by a rapid decay in light intensity” from the squid’s photogenic organ (pmc.ncbi.nlm.nih.gov). In fact, kinetic analysis in vivo suggested two light-emitting components: a fast-decaying component and a second slightly longer-lasting component (pmc.ncbi.nlm.nih.gov). This could indicate the presence of two populations of chromophores or enzyme states – possibly due to symplectin acting as a dimer or multiple symplectin isoforms. Regardless, the light emission is transient, on the order of seconds or less, which is consistent with a photoprotein that releases all its stored energy in a single burst. The emission spectrum peaks at ~470 nm (blue light) (pmc.ncbi.nlm.nih.gov), a wavelength that likely penetrates well in the open ocean and matches the sensitivity of many marine visual systems (predators/prey).

Catalytic Residues and Activity: Symplectin’s active site contains conserved residues analogous to those in biotinidase/pantetheinase. In human vanin-1 (pantetheinase), the catalytic triad is Glu-79, Lys-178, Cys-211 (pmc.ncbi.nlm.nih.gov). Sequence alignments show that two of these (the Glu and Lys) are invariant in virtually all symplectin homologs across taxa (pmc.ncbi.nlm.nih.gov). The nucleophilic cysteine in that triad is generally conserved as well, although in a few squid sequences it is naturally substituted (e.g., one Dosidicus gigas homolog has a serine in place of the catalytic Cys) (pmc.ncbi.nlm.nih.gov). In symplectin itself, the analogous cysteine is present (and distinct from the DCZ-binding Cys-390). The conservation of this triad strongly suggests that symplectin retains enzymatic (hydrolase) activity apart from luminescence (pmc.ncbi.nlm.nih.gov). In other words, symplectin has the structural capacity to function as an amidase, potentially cleaving substrates like biotinyl-peptides or pantetheine. There is evidence from related organisms that family members act as biotinidases: for example, a biotinidase activity was detected in Drosophila homologs of this family (pmc.ncbi.nlm.nih.gov). This has led experts to propose that the ancestral function of symplectin-like proteins was in biotin/vitamin B₅ metabolism, and the bioluminescent chemistry is a derived, neofunctionalized role (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Symplectin’s active site residues (including those for pantetheinase catalysis) are intact across essentially all known copies, implying that even the luminescent symplectin in squid may still catalyze a hydrolase reaction (though possibly at lower efficiency or in a different cellular context) (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Thus, symplectin might be a multi-functional enzyme, combining a metabolic enzyme’s chemistry with a novel light-producing capability.

Localization and Biological Role in the Squid

Photophore and Cellular Localization: In S. oualaniensis, symplectin is highly localized to a specialized light organ (photophore). This organ is a large yellow photogenic organ in the squid’s mantle (dorsal surface), containing thousands of tiny oval granules visible under microscopy (pmc.ncbi.nlm.nih.gov). Symplectin protein is concentrated within these granules. Biochemical fractionation showed that the essential light-emitting components are membrane-bound within the granules (pmc.ncbi.nlm.nih.gov). This strongly suggests that symplectin is associated with membranes, likely through a GPI anchor as mentioned above, anchoring it to granule vesicle membranes or luminal face of a membrane-bound compartment. Indeed, extraction experiments found symplectin in the high-salt soluble fraction of photophore homogenates only when using buffers that release peripheral membrane proteins (pubmed.ncbi.nlm.nih.gov), and early studies noted a free sulfhydryl (thiol) group is essential for activity, consistent with a cysteine (likely Cys-390) needing to be in the reduced state (pmc.ncbi.nlm.nih.gov) (if symplectin were improperly folded or disulfide-bonded in extraction, activity was lost). Each granule can be thought of as a bioluminescent micro-reactor: symplectin with its bound luciferin is packed inside, awaiting a signal.

Triggering Mechanism: The natural trigger for symplectin’s luminescent reaction is tied to ionic signals. Notably, the photoprotein is not Ca²⁺-activated, unlike many other photoproteins (e.g., aequorin). Instead, it responds to monovalent cations. Experiments by Tsuji & Leisman (1981) showed that exposing intact granules or granule homogenates to certain ions induces light emission: potassium (K⁺) is the most effective trigger, followed by Rb⁺, Na⁺, Cs⁺, NH₄⁺, and Li⁺ (in descending order of effectiveness) (pmc.ncbi.nlm.nih.gov). Divalent cations like Ca²⁺, Mg²⁺, or Sr²⁺ did not trigger light (pmc.ncbi.nlm.nih.gov). The optimal salt concentration for activation was around 0.6 M KCl or NaCl, at a slightly alkaline pH ~7.8 (pmc.ncbi.nlm.nih.gov). These findings indicate that a depolarization or osmotic shock mechanism is likely at play: in the living squid, a nerve impulse could cause a local surge in K⁺ or Na⁺ concentration around the photophore cells, mimicking the experimental high-K⁺ treatment. This would initiate the photoprotein’s breakdown of coelenterazine and the emission of a light flash. In essence, symplectin is under neurological control – the squid likely flashes its light organ by nervous stimulation that alters ion concentrations, rather than by a simple binding of Ca²⁺. This K⁺-triggered bioluminescence system is unusual and was one of the distinctive features noted in the first description of the squid’s luminescent organ (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

Biological Function (Ecological Role): Bioluminescence in squids serves various ecological purposes, and in S. oualaniensis it is believed to function primarily in defense and possibly intraspecific signaling. The S. oualaniensis photophore produces an intense, blinding flash of blue light (pmc.ncbi.nlm.nih.gov). Many midwater animals use bright flashes to startle or distract predators – a sudden flash can disorient predators or attract even larger predators to the scene, giving the squid a chance to escape (www.sciencedirect.com). In fact, some related squids and shrimp will even eject luminescent secretions as decoys (www.sciencedirect.com), although S. oualaniensis appears to keep its light contained to the organ (there is no evidence of it releasing the luminescent substance externally). The placement of the photophore (dorsal mantle) suggests it could also be used for counter-illumination camouflage or signaling to other squids above or beside the animal, but the startle-flash hypothesis is strongly supported by the nature of the luminescence (single, bright flashes rather than sustained glows). The organ’s yellow coloration and grouping of granules might even act as a diffuser or lens to spread the light flash widely. Thus, symplectin enables the squid to produce biologically meaningful light signals – likely a predator avoidance mechanism in the dim midwater environment (www.sciencedirect.com). This is a “real-world” implementation of the symplectin gene’s function: it directly contributes to survival behaviors in the squid’s natural habitat by providing a chemical means of generating light.

It’s worth noting that symplectin’s ancestral metabolic role (e.g. biotin scavenging) might still be relevant in non-luminous tissues of the squid. The gene encoding symplectin (sympp) could be expressed at low levels outside the photophore to perform standard enzymatic duties (such as recycling biotin or pantothenate), as suggested by the enzyme’s retained active-site conservation (pmc.ncbi.nlm.nih.gov). However, in the photogenic organ, the protein is highly expressed and specifically adapted to interact with coelenterazine for light production (pmc.ncbi.nlm.nih.gov). This dual functionality would parallel cases in other organisms where a single gene product has both routine metabolic function and a specialized role (in this case, bioluminescence) depending on context.

Evolutionary Insights and Recent Research Developments

Symplectin is an intriguing example of evolutionary neofunctionalization. It originates from a gene family that is ubiquitous in animals for metabolic processes, yet in certain squids it has duplicated and diverged to support bioluminescence (pmc.ncbi.nlm.nih.gov). Recent comparative genomic and transcriptomic studies (2010s) have shed light on how widespread the symplectin-like proteins are and how bioluminescent species diverged:

Gene Family Distribution: Most animals (from sponges and jellyfish to vertebrates) possess only one or two homologs of this C-N hydrolase photoprotein family (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). For example, humans have two main homologs (biotinidase and vanin pantetheinases). In contrast, cephalopods – particularly squids and octopuses – show an expansion of this gene family. One 2017 analysis found four distinct clades of symplectin-related proteins in cephalopods (pmc.ncbi.nlm.nih.gov). These likely arose from gene duplications specific to cephalopod lineages. Symplectin itself corresponds to one of these clades, comprising the true photoproteins used for autogenic (self-produced) bioluminescence in squids (pmc.ncbi.nlm.nih.gov).
Occurrence in Non-luminous Species: Intriguingly, homologs of symplectin exist even in non-bioluminescent cephalopods. For instance, the squid Loligo vulgaris, Doryteuthis pealeii, and the cuttlefish Sepia pharaonis all have symplectin-like genes (pmc.ncbi.nlm.nih.gov) despite these species not having known light organs. This suggests the core enzyme was present ancestrally (likely as a biotinidase) and only some descendants evolved the light-producing capability. In bioluminescent squids, one copy of the gene acquired mutations that enabled coelenterazine binding and light emission, while other copies might have retained classical enzymatic roles (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). The presence of the critical chromophore-binding cysteine (Cys-390) in nearly all homologs (luminous or not) indicates that the potential for photoprotein activity was a latent trait, realized in certain lineages by additional adaptations (pmc.ncbi.nlm.nih.gov).
Key Amino Acid Changes: The evolution of symplectin’s luminescent function likely required changes outside the conserved active site. The 2017 study by Francis et al. noted that while the catalytic center remains conserved, other regions of the protein (loops, binding pocket shape, etc.) must have changed to accommodate the bulky coelenterazine chromophore and promote its oxidation (pmc.ncbi.nlm.nih.gov). A specific cysteine (the one binding coelenterazine) is “critical for symplectin functioning” and is uniquely positioned: sequence alignments show a small insertion/deletion near that region unique to symplectin and its closest relatives (pmc.ncbi.nlm.nih.gov). These subtle sequence differences delineate the photoprotein clade from the ordinary enzymes. In Watasenia scintillans (the firefly squid, which uses a different luciferase system), researchers found multiple C-N hydrolase homologs, including two in the symplectin subgroup, but Watasenia primarily employs an unrelated luciferase for its light organ (pmc.ncbi.nlm.nih.gov). This underscores that cephalopods evolved bioluminescence convergently: even within squids, different species co-opted different enzymes for light production. Symplectin is the solution in S. oualaniensis and its relatives, whereas other squids have independently evolved luminescence using other protein families (pmc.ncbi.nlm.nih.gov).
Recent Research (2020s): New sequencing and proteomic studies continue to refine our understanding. A 2014 transcriptomic analysis of squid light organs (Pankey et al., PNAS 2014) identified symplectin transcripts among the highest-expressed genes in luminescent organs, supporting its central role in light emission. In 2016, Gimenez et al. showed via mass spectrometry and sequencing that even “glowing squid crystal proteins” (referring to reflective or structural photophore proteins in certain squids) belong to the same superfamily as firefly luciferase and possibly share distant ancestry with symplectin’s family (pmc.ncbi.nlm.nih.gov). In 2017, Francis et al. (PeerJ 2017) provided a comprehensive evolutionary study of symplectin, confirming the gene’s origin via duplications and highlighting that symplectin evolved through neo-functionalization in bioluminescent squids (pmc.ncbi.nlm.nih.gov). This research also pointed out that symplectin/pantetheinase-like genes are absent in certain non-bilaterian groups (e.g. ctenophores), hinting at interesting patterns of gene loss and gain in animal evolution (pmc.ncbi.nlm.nih.gov).
Conservation vs. Innovation: Overall, recent expert analysis agrees that symplectin’s luminescent function was grafted onto a highly conserved enzyme scaffold. As one study summarized, “symplectin may have multiple functions including hydrolase activity, and the evolution of the luminous phenotype required changes in the protein outside of the main binding pocket.” (pmc.ncbi.nlm.nih.gov). In other words, nature “kept” the enzyme’s original catalytic machinery intact while innovating around it to create a new biochemical phenotype (light emission).

Expert Commentary and Ongoing Significance

Symplectin has attracted interest as a biochemical curiosity – a hybrid of metabolism and luminescence. Biochemists in the early 2000s biochemically characterized symplectin, with Minoru Isobe and colleagues isolating the protein and its chromophore. By 2008 they confirmed the chromophore’s attachment site (Cys-390) and demonstrated how the bound dehydrocoelenterazine is the source of light (pmc.ncbi.nlm.nih.gov). These pioneering studies (Isobe et al., 2008 in Proc. Jpn. Acad. B) established the basic mechanism of symplectin’s photochemistry. Evolutionary biologists later recognized symplectin as a prime example of gene duplication leading to novel function. A 2010 review on marine bioluminescence noted symplectin as a “novel photoprotein from an oceanic squid… with sequence similarity to mammalian C-N hydrolases” (www.annualreviews.org), underscoring how a common enzyme family was co-opted for light production. Recent reviews (2023) on cephalopod bioluminescence cite symplectin’s discovery and highlight that squids have evolved multiple strategies (symbiotic bacteria in some, intrinsic enzymes like symplectin in others) to achieve bioluminescence (www.frontiersin.org) (pmc.ncbi.nlm.nih.gov). This makes symplectin a valuable case study in the field of evolutionary biochemistry and marine biology.

From an applications standpoint, symplectin itself is not yet widely used in biotechnology or medicine – in contrast to well-known luciferases (like firefly or Renilla luciferase) and photoproteins (like aequorin) which are popular research tools. However, understanding symplectin deepens our catalog of luciferase chemistries. Its unusual K⁺-triggered mechanism could inspire new types of bioassays or optogenetic switches that respond to ionic changes rather than calcium or ATP. Additionally, symplectin’s dual functionality (metabolic enzyme and light generator) provides insights into how enzymes can be engineered or repurposed. The fact that symplectin produces a quick flash rather than a sustained glow might be advantageous in designing reporters for fast signaling events. Any future attempt to harness symplectin would likely involve recombinant expression and reconstitution with coelenterazine – a challenging but potentially rewarding endeavor given the enzyme’s high light output and unique control. At the very least, symplectin adds to the repertoire of known luciferases and enriches our understanding of biochemical diversity in nature’s light-emitting systems.

Key Takeaways and Data Highlights

Identity: Symplectin is a ~60 kDa photoprotein enzyme encoded by the sympp gene in S. oualaniensis, responsible for that squid’s self-generated bioluminescence (pmc.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov). It is part of the nitrilase superfamily (carbon-nitrogen hydrolases) and is homologous to biotinidases and pantetheinases in other animals (pmc.ncbi.nlm.nih.gov).
Function: It catalyzes the oxidation of coelenterazine (a luciferin) to produce blue light (~470 nm) (pmc.ncbi.nlm.nih.gov). The luciferin is held in the protein as dehydrocoelenterazine-Cys adduct until use (pmc.ncbi.nlm.nih.gov). The light-emitting reaction requires oxygen and results in decarboxylation of the substrate, emitting CO₂ and a photon (pmc.ncbi.nlm.nih.gov).
Active Site and Mechanism: Contains the typical E–K–C catalytic triad of its enzyme family (pmc.ncbi.nlm.nih.gov), and a special cysteine (Cys-390) that covalently binds the chromophore (pmc.ncbi.nlm.nih.gov). Upon an appropriate trigger, the enzyme undergoes a conformational change or chemical step that leads to the chromophore’s oxidative breakdown and light release. A free thiol on the enzyme is essential for activity (thiol-blocking abolishes luminescence) (pmc.ncbi.nlm.nih.gov).
Localization: Found in the photogenic organ (light organ) of the squid, specifically in subcellular granules that likely correspond to modified secretory vesicles (pmc.ncbi.nlm.nih.gov). Symplectin is membrane-bound in these granules, probably via a GPI anchor (pmc.ncbi.nlm.nih.gov). The photophore is under neural control.
Triggering: Uniquely activated by K⁺/Na⁺ ions (and analogues like Rb⁺), not by Ca²⁺ (pmc.ncbi.nlm.nih.gov). In vivo, nerve stimulation causes ion fluxes that elicit a bright but brief flash of light (an all-or-none response). Optimal pH for light emission is ~7.8, matching physiological conditions (pmc.ncbi.nlm.nih.gov).
Biological role: Serves as a defensive flash mechanism to startle predators or as a means of communication with conspecifics in the dark ocean environment (www.sciencedirect.com). The flash’s intensity and brevity suggest an evolutionary role in predator avoidance (a form of counter-predation strategy).
Evolution: Symplectin evolved from a common biotinidase-like ancestor. Cephalopods have multiple symplectin-like genes due to duplications; only some (like symplectin itself) acquired bioluminescent functionality through key mutations (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). The protein retains ancestral enzymatic features (possibly still capable of vitamin-related hydrolysis) (pmc.ncbi.nlm.nih.gov), demonstrating an example of a gene with bifunctional potential.
Recent research: (2023) Reviews in marine science reiterate the importance of symplectin in cephalopod bioluminescence and note that research interest in squid bioluminescence has grown, with S. oualaniensis being among the studied species (www.frontiersin.org). The most recent molecular studies (2016–2017) resolved how widely the symplectin/pantetheinase family is distributed and conserved critical residues, reinforcing our current understanding of its mechanism (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).

In summary, symplectin (sympp) is a membrane-associated enzymatic protein that combines the chemistry of a hydrolase with the ability to emit light, enabling the purpleback flying squid to generate controlled bioluminescent flashes. It exemplifies how a conserved metabolic enzyme can be evolutionarily repurposed into a luciferase, illustrating nature’s ingenuity in biochemical innovation (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Ongoing studies of symplectin and its relatives continue to illuminate (literally and figuratively) both the molecular mechanism of light production in squids and the evolutionary pathways by which new protein functions arise.

References:

Fujii et al. (2002) – Biochem. Biophys. Res. Commun. 293(2):874–879. DOI: 10.1016/S0006-291X(02)00296-6. (Discovery of symplectin; sequence similarity to C-N hydrolases) (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).
Isobe et al. (2008) – Proc. Japan Acad. B 84(9):386–392. Published Nov 2008. DOI: 10.2183/pjab/84.386. (Identified Cys-390 as the luciferin-binding site via mass spectrometry) (pmc.ncbi.nlm.nih.gov).
Tsuji & Leisman (1981) – PNAS 78(11):6719–6723. (Characterized K⁺/Na⁺-triggered luminescence in S. oualaniensis photophores; ionic triggering and O₂ requirement) (pmc.ncbi.nlm.nih.gov).
Haddock et al. (2010) – Ann. Rev. Marine Science 2:443–493. (General review of bioluminescence in the sea; mentions symplectin and other systems) (www.annualreviews.org).
Francis et al. (2017) – PeerJ 5:e3633. Published Jul 31 2017. DOI: 10.7717/peerj.3633. (Comparative study of symplectin/pantetheinase family in luminous and non-luminous squids; evolutionary analysis) (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).
Frontiers in Marine Science (2023) – 10:1161049 (Review on cephalopod bioluminescence; coverage of diversity and research trends in squid luminescence) (www.sciencedirect.com) (www.frontiersin.org).

Citations

AnnotationURLCitation(end_index=581, start_index=413, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=The%20squid%20Sthenoteuthis%20oualaniensis%2C%20formerly,While%20the%20majority%20of')
AnnotationURLCitation(end_index=1044, start_index=898, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20of,as%20shown%20in%20%209')
AnnotationURLCitation(end_index=1381, start_index=1213, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=The%20squid%20Sthenoteuthis%20oualaniensis%2C%20formerly,While%20the%20majority%20of')
AnnotationURLCitation(end_index=1539, start_index=1382, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=To%20better%20understand%20the%20relative,based%20on%20the%20genomes%20of')
AnnotationURLCitation(end_index=1845, start_index=1676, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=as%20sequence%20isolates%20with%20few,for%20symplectin%20functioning%20is%20conserved')
AnnotationURLCitation(end_index=2111, start_index=1954, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=To%20better%20understand%20the%20relative,based%20on%20the%20genomes%20of')
AnnotationURLCitation(end_index=2488, start_index=2367, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=match%20at%20L351%20al,The%20cysteine')
AnnotationURLCitation(end_index=2794, start_index=2661, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=the%20human%20protein%20vanin,1%20%28Boersma%20et')
AnnotationURLCitation(end_index=3164, start_index=3024, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=et%20al.%2C%202014%29.%20Head,have%20a%20role%20in%20the')
AnnotationURLCitation(end_index=4175, start_index=4027, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=It%20is%20clear%20from%20the,copy%20number%20in%20that%20species')
AnnotationURLCitation(end_index=4395, start_index=4313, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/18997450/#:~:text=Fig')
AnnotationURLCitation(end_index=4922, start_index=4777, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=in%20green%2C%20while%20the%20one,is%20instead%20a%20cysteine')
AnnotationURLCitation(end_index=5097, start_index=4923, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20from,symplectin%20after%20luminescence%20showed%20the')
AnnotationURLCitation(end_index=5705, start_index=5531, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20from,symplectin%20after%20luminescence%20showed%20the')
AnnotationURLCitation(end_index=5982, start_index=5808, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20from,symplectin%20after%20luminescence%20showed%20the')
AnnotationURLCitation(end_index=6521, start_index=6375, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20of,as%20shown%20in%20%209')
AnnotationURLCitation(end_index=6895, start_index=6778, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=ortho,so%20as%20to%20emit%20light')
AnnotationURLCitation(end_index=7465, start_index=7283, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=potassium%2C%20rubidium%2C%20sodium%2C%20cesium%2C%20ammonium%2C,A%20free%20sulfhydryl%20group%20is')
AnnotationURLCitation(end_index=8223, start_index=8106, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=ortho,so%20as%20to%20emit%20light')
AnnotationURLCitation(end_index=8680, start_index=8506, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20from,symplectin%20after%20luminescence%20showed%20the')
AnnotationURLCitation(end_index=9087, start_index=8927, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=A%20distinctive%20type%20of%20luminescent,Analysis%20of%20the%20kinetics%20of')
AnnotationURLCitation(end_index=9420, start_index=9241, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=potassium%2C%20rubidium%2C%20sodium%2C%20cesium%2C%20ammonium%2C,The%20optimum%20KCl%20or%20NaCl')
AnnotationURLCitation(end_index=9958, start_index=9812, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20of,as%20shown%20in%20%209')
AnnotationURLCitation(end_index=10438, start_index=10317, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=match%20at%20L351%20al,The%20cysteine')
AnnotationURLCitation(end_index=10685, start_index=10564, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=match%20at%20L351%20al,The%20cysteine')
AnnotationURLCitation(end_index=11015, start_index=10906, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=Open%20in%20a%20new%20tab')
AnnotationURLCitation(end_index=11379, start_index=11250, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=symplectin,of%20the%20main%20binding%20pocket')
AnnotationURLCitation(end_index=11863, start_index=11709, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=both%20of%20these%20molecules%20is,the%20ancestral%20function%20is%20a')
AnnotationURLCitation(end_index=12218, start_index=12064, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=both%20of%20these%20molecules%20is,the%20ancestral%20function%20is%20a')
AnnotationURLCitation(end_index=12374, start_index=12219, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=First%2C%20one%20or%20many%20of,therefore%20is%20a%20derived%20function')
AnnotationURLCitation(end_index=12803, start_index=12674, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=symplectin,of%20the%20main%20binding%20pocket')
AnnotationURLCitation(end_index=12959, start_index=12804, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=First%2C%20one%20or%20many%20of,therefore%20is%20a%20derived%20function')
AnnotationURLCitation(end_index=13601, start_index=13455, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20of,as%20shown%20in%20%209')
AnnotationURLCitation(end_index=13906, start_index=13782, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=intensity,The%20optimum%20KCl%20or%20NaCl')
AnnotationURLCitation(end_index=14386, start_index=14294, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/18997450/#:~:text=SDS,%E2%80%A6')
AnnotationURLCitation(end_index=14711, start_index=14552, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=the%20decay%20of%20light%20intensity,group%20is%20essential%20for%20activity')
AnnotationURLCitation(end_index=15645, start_index=15482, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=Intact%20granules%20or%20washed%20homogenates,A%20free%20sulfhydryl%20group%20is')
AnnotationURLCitation(end_index=15869, start_index=15713, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=Intact%20granules%20or%20washed%20homogenates,emitting%20components%20are')
AnnotationURLCitation(end_index=16165, start_index=15978, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=potassium%2C%20rubidium%2C%20sodium%2C%20cesium%2C%20ammonium%2C,group%20is%20essential%20for%20activity')
AnnotationURLCitation(end_index=17042, start_index=16882, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=A%20distinctive%20type%20of%20luminescent,Analysis%20of%20the%20kinetics%20of')
AnnotationURLCitation(end_index=17206, start_index=17043, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=Intact%20granules%20or%20washed%20homogenates,A%20free%20sulfhydryl%20group%20is')
AnnotationURLCitation(end_index=17676, start_index=17516, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=A%20distinctive%20type%20of%20luminescent,Analysis%20of%20the%20kinetics%20of')
AnnotationURLCitation(end_index=18031, start_index=17880, title='Marine Optics: Dark Disguise - ScienceDirect', type='url_citation', url='https://www.sciencedirect.com/science/article/pii/S096098221101133X#:~:text=Luminescence%20is%20used%20for%20other,but%20not')
AnnotationURLCitation(end_index=18273, start_index=18122, title='Marine Optics: Dark Disguise - ScienceDirect', type='url_citation', url='https://www.sciencedirect.com/science/article/pii/S096098221101133X#:~:text=Luminescence%20is%20used%20for%20other,but%20not')
AnnotationURLCitation(end_index=19184, start_index=19033, title='Marine Optics: Dark Disguise - ScienceDirect', type='url_citation', url='https://www.sciencedirect.com/science/article/pii/S096098221101133X#:~:text=Luminescence%20is%20used%20for%20other,but%20not')
AnnotationURLCitation(end_index=19938, start_index=19783, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=First%2C%20one%20or%20many%20of,therefore%20is%20a%20derived%20function')
AnnotationURLCitation(end_index=20239, start_index=20084, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=as%20sequence%20isolates%20with%20few,even%20those%20unlikely%20to%20be')
AnnotationURLCitation(end_index=20907, start_index=20752, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=as%20sequence%20isolates%20with%20few,even%20those%20unlikely%20to%20be')
AnnotationURLCitation(end_index=21415, start_index=21248, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=use%20of%20publicly%20available%20but,may%20have%20multiple%20functions%20including')
AnnotationURLCitation(end_index=21548, start_index=21416, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=identity,However%2C%20hemichordates%20are%20only')
AnnotationURLCitation(end_index=22008, start_index=21830, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=symplectin%2Fpantetheinase%20protein%20family%20in%20Metazoa,even%20those%20unlikely%20to%20be')
AnnotationURLCitation(end_index=22401, start_index=22234, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=use%20of%20publicly%20available%20but,may%20have%20multiple%20functions%20including')
AnnotationURLCitation(end_index=22800, start_index=22663, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=Among%20the%20four%20cephalopod%20protein,scintillans')
AnnotationURLCitation(end_index=23328, start_index=23191, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=Among%20the%20four%20cephalopod%20protein,scintillans')
AnnotationURLCitation(end_index=23484, start_index=23329, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=First%2C%20one%20or%20many%20of,therefore%20is%20a%20derived%20function')
AnnotationURLCitation(end_index=23886, start_index=23733, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=spiralians%20have%20one%20or%20two,of%20the%20main%20binding%20pocket')
AnnotationURLCitation(end_index=24411, start_index=24282, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=symplectin,of%20the%20main%20binding%20pocket')
AnnotationURLCitation(end_index=24760, start_index=24651, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=Open%20in%20a%20new%20tab')
AnnotationURLCitation(end_index=25264, start_index=25117, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=protein,they%20have%20photoprotein%20activity%20with%C2%A0dhCtz')
AnnotationURLCitation(end_index=25733, start_index=25586, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=protein,they%20have%20photoprotein%20activity%20with%C2%A0dhCtz')
AnnotationURLCitation(end_index=26513, start_index=26372, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=%5BPubMed%5D%20%5BGoogle%20Scholar%5D%20,Google%20Scholar')
AnnotationURLCitation(end_index=26944, start_index=26759, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=symplectin%2Fpantetheinase%20protein%20family%20in%20Metazoa,active%20site%20residues%20involved%20in')
AnnotationURLCitation(end_index=27288, start_index=27156, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=identity,However%2C%20hemichordates%20are%20only')
AnnotationURLCitation(end_index=27823, start_index=27670, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=spiralians%20have%20one%20or%20two,of%20the%20main%20binding%20pocket')
AnnotationURLCitation(end_index=28600, start_index=28437, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20from,luminescence%20by%2012%20mass%20units')
AnnotationURLCitation(end_index=29168, start_index=29019, title='Bioluminescence in the Sea | Annual Reviews', type='url_citation', url='https://www.annualreviews.org/doi/10.1146/annurev-marine-120308-081028#:~:text=match%20at%20L372%20novel%20photoprotein,In')
AnnotationURLCitation(end_index=29690, start_index=29489, title='Frontiers | Bioluminescence in cephalopods: biodiversity, biogeography and research trends', type='url_citation', url='https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1161049/full#:~:text=research%20trends%20www,Cephalopods%20in%20the%20Anthropocene%3A%20Multiple')
AnnotationURLCitation(end_index=29838, start_index=29691, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=protein,they%20have%20photoprotein%20activity%20with%C2%A0dhCtz')
AnnotationURLCitation(end_index=31497, start_index=31351, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20of,as%20shown%20in%20%209')
AnnotationURLCitation(end_index=31610, start_index=31498, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PubMed', type='url_citation', url='https://pubmed.ncbi.nlm.nih.gov/18997450/#:~:text=SDS,KCl%20extract%20at%2060%20kDa')
AnnotationURLCitation(end_index=31908, start_index=31751, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=To%20better%20understand%20the%20relative,based%20on%20the%20genomes%20of')
AnnotationURLCitation(end_index=32172, start_index=32026, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20of,as%20shown%20in%20%209')
AnnotationURLCitation(end_index=32433, start_index=32259, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20from,symplectin%20after%20luminescence%20showed%20the')
AnnotationURLCitation(end_index=32671, start_index=32554, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=ortho,so%20as%20to%20emit%20light')
AnnotationURLCitation(end_index=32896, start_index=32775, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=match%20at%20L351%20al,The%20cysteine')
AnnotationURLCitation(end_index=33147, start_index=32973, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20from,symplectin%20after%20luminescence%20showed%20the')
AnnotationURLCitation(end_index=33567, start_index=33408, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=the%20decay%20of%20light%20intensity,group%20is%20essential%20for%20activity')
AnnotationURLCitation(end_index=33893, start_index=33747, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20of,as%20shown%20in%20%209')
AnnotationURLCitation(end_index=34093, start_index=33969, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=intensity,The%20optimum%20KCl%20or%20NaCl')
AnnotationURLCitation(end_index=34393, start_index=34230, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=Intact%20granules%20or%20washed%20homogenates,A%20free%20sulfhydryl%20group%20is')
AnnotationURLCitation(end_index=34745, start_index=34586, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=the%20decay%20of%20light%20intensity,group%20is%20essential%20for%20activity')
AnnotationURLCitation(end_index=35064, start_index=34913, title='Marine Optics: Dark Disguise - ScienceDirect', type='url_citation', url='https://www.sciencedirect.com/science/article/pii/S096098221101133X#:~:text=Luminescence%20is%20used%20for%20other,but%20not')
AnnotationURLCitation(end_index=35600, start_index=35445, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=as%20sequence%20isolates%20with%20few,even%20those%20unlikely%20to%20be')
AnnotationURLCitation(end_index=35738, start_index=35601, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=Among%20the%20four%20cephalopod%20protein,scintillans')
AnnotationURLCitation(end_index=35999, start_index=35844, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=First%2C%20one%20or%20many%20of,therefore%20is%20a%20derived%20function')
AnnotationURLCitation(end_index=36550, start_index=36314, title='Frontiers | Bioluminescence in cephalopods: biodiversity, biogeography and research trends', type='url_citation', url='https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1161049/full#:~:text=tasmanica%2C%20Watasenia%20scintillans%2C%20Sthenoteuthis%20oualanienesis,species%20or%20groups%20of%20species')
AnnotationURLCitation(end_index=36924, start_index=36757, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=use%20of%20publicly%20available%20but,may%20have%20multiple%20functions%20including')
AnnotationURLCitation(end_index=37094, start_index=36925, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=proteins%2C%20suggesting%20that%20symplectin%20may,of%20the%20main%20binding%20pocket')
AnnotationURLCitation(end_index=37683, start_index=37498, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=symplectin%2Fpantetheinase%20protein%20family%20in%20Metazoa,active%20site%20residues%20involved%20in')
AnnotationURLCitation(end_index=37839, start_index=37684, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=First%2C%20one%20or%20many%20of,therefore%20is%20a%20derived%20function')
AnnotationURLCitation(end_index=38422, start_index=38265, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=To%20better%20understand%20the%20relative,based%20on%20the%20genomes%20of')
AnnotationURLCitation(end_index=38528, start_index=38423, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=,Scientific%20Reports')
AnnotationURLCitation(end_index=38878, start_index=38715, title='Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC3721202/#:~:text=Symplectin%20is%20a%20photoprotein%20from,luminescence%20by%2012%20mass%20units')
AnnotationURLCitation(end_index=39221, start_index=39053, title='K+/Na+-triggered bioluminescence in the oceanic squid Symplectoteuthis oualaniensis - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC349121/#:~:text=Intact%20granules%20or%20washed%20homogenates,group%20is%20essential%20for%20activity')
AnnotationURLCitation(end_index=39527, start_index=39378, title='Bioluminescence in the Sea | Annual Reviews', type='url_citation', url='https://www.annualreviews.org/doi/10.1146/annurev-marine-120308-081028#:~:text=match%20at%20L372%20novel%20photoprotein,In')
AnnotationURLCitation(end_index=39924, start_index=39739, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=symplectin%2Fpantetheinase%20protein%20family%20in%20Metazoa,active%20site%20residues%20involved%20in')
AnnotationURLCitation(end_index=40062, start_index=39925, title='Symplectin evolved from multiple duplications in bioluminescent squid - PMC', type='url_citation', url='https://pmc.ncbi.nlm.nih.gov/articles/PMC5541922/#:~:text=Among%20the%20four%20cephalopod%20protein,scintillans')
AnnotationURLCitation(end_index=40374, start_index=40223, title='Marine Optics: Dark Disguise - ScienceDirect', type='url_citation', url='https://www.sciencedirect.com/science/article/pii/S096098221101133X#:~:text=Luminescence%20is%20used%20for%20other,but%20not')
AnnotationURLCitation(end_index=40611, start_index=40375, title='Frontiers | Bioluminescence in cephalopods: biodiversity, biogeography and research trends', type='url_citation', url='https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1161049/full#:~:text=tasmanica%2C%20Watasenia%20scintillans%2C%20Sthenoteuthis%20oualanienesis,species%20or%20groups%20of%20species')