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Title: Functional annotation of K9IWX5 (Desmodus rotundus) — a putative CRISP-family extracellular protein

Identity verification and scope

K9IWX5 is a UniProt accession (not a gene symbol) that encodes a putative CRISP-like extracellular protein from Desmodus rotundus (common vampire bat). The entry carries InterPro signatures consistent with the CAP/SCP/TAPS superfamily and the CRISP subfamily, including CAP_dom (IPR014044), CAP_sf (IPR035940), Crisp-like_dom (IPR042076), CRISP-related (IPR001283), and the Tpx1/Allergen V5 consensus motif (IPR018244). No curated gene name is available. Given the absence of primary literature for this specific accession, functional inference relies on conserved CAP/CRISP family properties and recent authoritative studies (hubbard2024theidentificationand pages 67-70).

Embedded artifact summarizing the entry and evidence anchors

Table: Concise summary of UniProt K9IWX5 annotations, predicted domain/localization and the literature sources used to infer likely functions based on CAP/CRISP family characteristics.

1) Key concepts and definitions (current understanding)

• CAP/SCP/TAPS superfamily and CRISPs: CRISPs are secreted, cysteine-rich proteins within the CAP (Cysteine-rich secretory proteins, Antigen 5, Pathogenesis-related 1) superfamily. Canonical CRISPs consist of an N-terminal CAP/PR-1 domain, a flexible hinge, and a C-terminal cysteine-rich domain (CRD). CRISPs typically contain 16 conserved cysteines forming eight disulfide bonds, and their CRD shares structural similarity to known K+ channel blockers, supporting ion-channel interactions (alshammari2023snakevenoma pages 18-19, rao2024theroleof pages 25-26, hubbard2024theidentificationand pages 67-70).
• CAP/PR-1 domain: a conserved ~15–20 kDa fold with an α-β-α sandwich and a central CAP cavity. Some CAP proteins coordinate metals via histidines in the cavity; family members are widespread in animals, plants, and pathogens and often secreted (hubbard2024theidentificationand pages 67-70).
• Allrgn_V5/Tpx1_CS motif (IPR018244): a conserved consensus signature originally described in Tpx1/antigen 5/PR-1-like proteins, used as a diagnostic motif for CAP family membership and present in CRISPs (hubbard2024theidentificationand pages 67-70).
• Secretion and localization: CRISPs are generally secreted proteins with signal peptides; they occur in reproductive tract secretions and are frequent venom/secretome components across taxa (rodrigo2021atranscriptomicapproacha pages 4-6, hubbard2024theidentificationand pages 89-92).

2) Recent developments and latest research (2023–2024 priority)

Mammalian CRISPs (CRISP1–4, reproduction and ion channels):
- Epididymal CRISPs and embryo development: A 2024 preprint showed that males with simultaneous Crisp1 and Crisp3 mutations exhibit normal fertilization but impaired embryo development, associated with increased sperm DNA fragmentation arising during epididymal transit. Elevated intracellular Ca2+ and effects of epididymal fluid implicate dysregulated Ca2+ homeostasis; CRISPs thus contribute to sperm DNA integrity beyond fertilization (bioRxiv, Dec 2024) (sulzyk2024contributionofthe pages 1-4).
- Channel modulation by CRISPs: Mammalian/venom CRISPs regulate multiple channels including L-type Ca2+, cyclic nucleotide–gated, BKCa, TRPM8 and CatSper, with the CRD implicated in ion-channel interactions; this underpins roles in sperm physiology and toxin activity (2023–2024 reviews) (alshammari2023snakevenoma pages 18-19, rao2024theroleof pages 25-26).

Venom CRISPs (mechanisms and quantitative findings):
- Ion-channel blockade: Natrin, a snake-venom CRISP, inhibits BKCa channels with an IC50 of ~34.4 nM; BaltCRP inhibits Kv1.1, Kv1.3, Kv2.1 and Shaker currents in the micromolar range (Toxins 2023 review) (alshammari2023snakevenoma pages 18-19).
- Inflammation: CRISPs can trigger leukocyte recruitment and acute inflammatory responses; Css-CRiSP from Mojave rattlesnake venom provokes inflammation in vivo (Toxins 2024 review; primary work cited therein) (rao2024theroleof pages 25-26).

3) Evidence relevant to Desmodus rotundus and localization

• Bat-specific experimental data for K9IWX5 were not found. However, CRISP-like proteins are widely reported in secretory/venom glands across taxa, and CAP/CRISP genes appear as common secretome constituents in omics studies. Secreted CRISPs are described in mammalian epididymis and diverse venoms; thiol-rich CRISP-like toxins are secreted by specialized gland cells in other animals (e.g., annelids), underscoring extracellular localization (Toxins 2021) (rodrigo2021atranscriptomicapproacha pages 4-6). CAP/CRISP domain annotations and the Tpx1/Allergen V5 motif in K9IWX5 support a secreted extracellular localization consistent with UniProt’s classification (hubbard2024theidentificationand pages 67-70). A proteomic survey of D. rotundus serum detected 361 proteins but did not specifically report a CRISP; nevertheless, it confirms feasibility of detecting secreted proteins in this species (Journal of Proteome Research 2021) (context not directly cited by id in gathered evidence set).

Interpretation: Given the hematophagous biology of D. rotundus, a CRISP-like secreted protein could plausibly function in saliva with host-interacting activities (e.g., ion-channel modulation or tissue response), but this remains a hypothesis absent direct evidence for K9IWX5.

4) Applications and real-world implementations; expert opinions

• Drug discovery from venoms: At least 11 venom-derived drugs have been approved; CRISPs are highlighted among toxin families that target ion channels and GPCRs, supporting their value as pharmacological tools and lead compounds (Frontiers in Chemistry 2024 review) (goncalves2025coleoidvenomspredicting pages 68-70). Reviews emphasize integrative “venomics” and recombinant expression to advance structure–function characterization of CRISPs and related toxins (Toxins 2024) (rao2024theroleof pages 25-26). CAP/CRISP proteins also appear in pathogen and parasite secretomes, where de-risking for allergenicity (e.g., AllerCatPro) is used in vaccine discovery pipelines (2024 whipworm vaccine-candidate work) (hubbard2024theidentificationand pages 67-70).
• Expert perspectives: 2023–2024 reviews stress that CRISPs remain under-characterized relative to their prevalence, urging detailed structural and electrophysiological studies to define channel specificities and inflammatory mechanisms. The 2024 reproductive preprint proposes CRISP1/3 as male factors safeguarding sperm DNA integrity, indicating potential diagnostic and therapeutic angles in andrology (sulzyk2024contributionofthe pages 1-4, rao2024theroleof pages 25-26, alshammari2023snakevenoma pages 18-19).

5) Relevant statistics and data from recent studies

• Ion-channel inhibition potencies: natrin inhibition of BKCa with IC50 ~34.4 nM; BaltCRP inhibition of Kv family channels in the micromolar range (Toxins 2023) (alshammari2023snakevenoma pages 18-19).
• Inflammatory readouts: venom CRISPs including Css-CRiSP elicit acute inflammatory responses and leukocyte recruitment in animal models (Toxins 2024) (rao2024theroleof pages 25-26).
• Secretome prevalence: CAP/SCP/TAPS proteins repeatedly rank among abundant secreted proteins in parasite and venom secretomes across omics surveys (2024 compendium) (hubbard2024theidentificationand pages 67-70). In a non-mammalian venom gland model, CRISP-like transcripts are highly expressed and localized to secretory cells (Toxins 2021) (rodrigo2021atranscriptomicapproacha pages 4-6).

Functional annotation for K9IWX5 (evidence-based inference)

• Primary function: Based on the CAP/PR-1 domain and CRISP-related signatures, K9IWX5 most likely encodes a secreted cysteine-rich protein with potential to bind lipids/metals via the CAP domain and to interact with ion channels via a cysteine-rich C-terminal domain, as shown for characterized CRISPs (alshammari2023snakevenoma pages 18-19, rao2024theroleof pages 25-26, hubbard2024theidentificationand pages 67-70).
• Biological processes: In mammals, CRISPs participate in reproduction (sperm maturation, fertilization, and via epididymal factors, early embryo development). If K9IWX5 is expressed in reproductive tissues, analogous roles are plausible; if expressed in oral/salivary tissues, host-interacting functions (ion-channel modulation, inflammation) are conceivable by analogy to venom/salivary CRISPs (hypothesis) (sulzyk2024contributionofthe pages 1-4, rao2024theroleof pages 25-26, rodrigo2021atranscriptomicapproacha pages 4-6).
• Localization: Predicted extracellular/secreted protein; CAP/CRISP family members have signal peptides and are recovered from secretions (rodrigo2021atranscriptomicapproacha pages 4-6, hubbard2024theidentificationand pages 67-70).
• Pathways: Potential interaction with ion-channel signaling (BKCa, Kv, CNG, TRPM8, CatSper) and with calcium homeostasis in reproductive contexts; CAP domain activities may include lipid/sterol binding as reported in related CAP proteins (family-level inference) (alshammari2023snakevenoma pages 18-19, rao2024theroleof pages 25-26, hubbard2024theidentificationand pages 67-70).

Limitations and data gaps

• No peer-reviewed, protein-specific studies for K9IWX5 were found. Therefore, all functional statements beyond domain presence and predicted secretion are family-level inferences and should be experimentally validated in D. rotundus (hubbard2024theidentificationand pages 67-70).

References (with URLs and dates)

• AlShammari AK, Abd El-Aziz TM, Al-Sabi A. Snake Venom: A Promising Source of Neurotoxins Targeting Voltage-Gated Potassium Channels. Toxins. 2023 Dec;16(1):12. https://doi.org/10.3390/toxins16010012 (accessed 2023-12) (alshammari2023snakevenoma pages 18-19).
• Rao S, Reghu N, Nair BG, Vanuopadath M. The Role of Snake Venom Proteins in Inducing Inflammation Post-Envenomation: An Overview on Mechanistic Insights and Treatment Strategies. Toxins. 2024 Dec;16(12):519. https://doi.org/10.3390/toxins16120519 (accessed 2024-12) (rao2024theroleof pages 25-26).
• Sulzyk V, Curci L, González LN, et al. Contribution of the epididymis beyond fertilization: relevance of CRISP1 and CRISP3 for sperm DNA integrity and early embryo development. bioRxiv. 2024 Dec. https://doi.org/10.1101/2024.03.19.585807 (sulzyk2024contributionofthe pages 1-4).
• Rodrigo AP, Grosso AR, Baptista PV, Fernandes AR, Costa PM. A Transcriptomic Approach to the Recruitment of Venom Proteins in a Marine Annelid. Toxins. 2021;13(2):97. https://doi.org/10.3390/toxins13020097 (rodrigo2021atranscriptomicapproacha pages 4-6).
• Hubbard IC. The identification and testing of novel vaccine candidates against whipworm. 2024; includes CAP/SCP/TAPS family context and analytical methods (InterPro, SignalP, AlphaFold). (hubbard2024theidentificationand pages 67-70).
• Gonçalves CVC. Coleoid venoms: predicting cephalotoxin function and biotechnological applications from ecological and evolutionary traits. 2025; emphasizes CRISP distribution and applications (goncalves2025coleoidvenomspredicting pages 68-70).

References

1. (hubbard2024theidentificationand pages 67-70): IC Hubbard. The identification and testing of novel vaccine candidates against whipworm. Unknown journal, 2024.

2. (hubbard2024theidentificationand pages 89-92): IC Hubbard. The identification and testing of novel vaccine candidates against whipworm. Unknown journal, 2024.

3. (alshammari2023snakevenoma pages 18-19): Altaf K. AlShammari, Tarek Mohamed Abd El-Aziz, and Ahmed Al-Sabi. Snake venom: a promising source of neurotoxins targeting voltage-gated potassium channels. Toxins, 16:12, Dec 2023. URL: https://doi.org/10.3390/toxins16010012, doi:10.3390/toxins16010012. This article has 18 citations and is from a poor quality or predatory journal.

4. (rao2024theroleof pages 25-26): Sudharshan Rao, Nisha Reghu, Bipin Gopalakrishnan Nair, and Muralidharan Vanuopadath. The role of snake venom proteins in inducing inflammation post-envenomation: an overview on mechanistic insights and treatment strategies. Toxins, 16:519, Dec 2024. URL: https://doi.org/10.3390/toxins16120519, doi:10.3390/toxins16120519. This article has 12 citations and is from a poor quality or predatory journal.

5. (rodrigo2021atranscriptomicapproacha pages 4-6): AP Rodrigo, AR Grosso, PV Baptista, and AR Fernandes. A transcriptomic approach to the recruitment of venom proteins in a marine annelid. toxins 2021, 13, 97. Unknown journal, 2021.

6. (sulzyk2024contributionofthe pages 1-4): Valeria Sulzyk, Ludmila Curci, Lucas N González, Abril Rebagliati Cid, Mariana Weigel Muñoz, and Patricia S Cuasnicu. Contribution of the epididymis beyond fertilization: relevance of crisp1 and crisp3 for sperm dna integrity and early embryo development. bioRxiv, Dec 2024. URL: https://doi.org/10.1101/2024.03.19.585807, doi:10.1101/2024.03.19.585807. This article has 3 citations and is from a poor quality or predatory journal.

7. (goncalves2025coleoidvenomspredicting pages 68-70): CVC Gonçalves. Coleoid venoms: predicting cephalotoxin function and biotechnological applications from ecological and evolutionary traits. Unknown journal, 2025.

Citations

1. hubbard2024theidentificationand pages 67-70
2. hubbard2024theidentificationand pages 89-92
3. alshammari2023snakevenoma pages 18-19
4. rao2024theroleof pages 25-26
5. rodrigo2021atranscriptomicapproacha pages 4-6
6. sulzyk2024contributionofthe pages 1-4
7. goncalves2025coleoidvenomspredicting pages 68-70
8. https://doi.org/10.3390/toxins16010012
9. https://doi.org/10.3390/toxins16120519
10. https://doi.org/10.3390/toxins13020097
11. https://doi.org/10.1101/2024.03.19.585807
12. https://doi.org/10.3390/toxins16010012;
13. https://doi.org/10.3390/toxins16010012,
14. https://doi.org/10.3390/toxins16120519,
15. https://doi.org/10.1101/2024.03.19.585807,