GO Term	Evidence	Action	Reason
GO:0005576 extracellular region	IEA GO_REF:0000044	ACCEPT	Summary: SAHS2 is annotated to the extracellular region based on IEA mapping from UniProtKB subcellular location vocabulary. UniProt marks SAHS2 as "Secreted" based on similarity to SAHS1 (J7MFT5). The protein has a predicted signal peptide (residues 1-19) and was originally identified in the heat-soluble proteome of tardigrades (PMID:22937162). SAHS proteins are described as having a secretory localization distinct from the cytoplasmic CAHS family (PMID:22937162). The annotation to GO:0005576 extracellular region is well supported. Reason: SAHS2 has a signal peptide and is described as a secretory protein. The original proteomics study identified SAHS proteins as having distinct subcellular localization from CAHS proteins, with SAHS being secretory (PMID:22937162). The name itself (Secretory Abundant Heat Soluble) reflects this localization. Extracellular region is the appropriate GO CC term for a secreted protein. Supporting Evidence: PMID:22937162 We named them Cytoplasmic Abundant Heat Soluble (CAHS) and Secretory Abundant Heat Soluble (SAHS) protein families, according to their localization. PMID:28703282 Secretory abundant heat-soluble (SAHS) proteins have been reported as candidates for anhydrobiosis-related proteins in tardigrades, which seem to protect extracellular components and/or secretory organelles.
GO:0008289 lipid binding	ISS PMID:28703282 Structural insights into a secretory abundant heat-soluble p...	NEW	Summary: SAHS2 is not currently annotated with lipid binding in GOA, but structural studies of the paralog SAHS1 (RvSAHS1) demonstrate that SAHS proteins adopt a beta-barrel fold homologous to fatty acid-binding proteins (FABPs) with two putative ligand binding sites (PMID:28703282). CDD classifies SAHS2 as containing an FABP domain (cd00742), InterPro assigns calycin fold (IPR012674), and SUPFAM classifies it in the Lipocalin superfamily (SSF50814). Crystal structure of SAHS4 showed variant binding preferences at these sites (PMID:29493034), suggesting functional diversification within the SAHS family. Reason: Although no direct lipid binding assay has been performed on SAHS2 specifically, the structural evidence from the SAHS1 crystal structure (PMID:28703282) combined with the FABP domain classification (CDD cd00742) and calycin/lipocalin superfamily membership strongly supports lipid binding as a molecular function. SAHS1 (J7MFT5) already has an IEA lipid binding annotation via InterPro. The same structural basis applies to SAHS2, which shares the conserved SAHS domains and FABP-like fold. ISS evidence from the paralog SAHS1 crystal structure is appropriate. Supporting Evidence: PMID:28703282 RvSAHS1 shows a beta-barrel structure similar to fatty acid-binding proteins (FABPs), in which hydrophilic residues form peculiar hydrogen bond networks... We identified two putative ligand-binding sites: one that superimposes on those of some FABPs and the other, unique to and conserved in SAHS proteins. These results indicate that SAHS proteins constitute a new FABP family. PMID:29493034 A previous crystallographic study revealed that a SAHS protein (RvSAHS1) from one of the toughest tardigrades, Ramazzottius varieornatus, has a beta-barrel architecture similar to fatty acid binding proteins (FABPs) and two putative ligand binding sites (LBS1 and LBS2) where fatty acids can bind.
GO:0009269 response to desiccation	IDA PMID:22937162 Two novel heat-soluble protein families abundantly expressed...	NEW	Summary: SAHS proteins were discovered through heat-soluble proteomics specifically aimed at identifying desiccation tolerance factors in tardigrades (PMID:22937162). SAHS2 changes conformation from beta-structure to alpha-helical structure under water-deficient conditions, similar to LEA proteins, suggesting a direct protective role during desiccation. The protein is constitutively and abundantly expressed, consistent with the fact that R. varieornatus tolerates rapid desiccation without significant transcriptional regulation (PMID:27649274). UniProt annotates SAHS2 as acting as a molecular shield in water-deficient conditions. Reason: Response to desiccation (GO:0009269) is a core biological process for SAHS2. The protein was identified specifically in the context of anhydrobiosis research, changes conformation under desiccating conditions, and is proposed to function as a molecular shield protecting extracellular components during desiccation. The evidence from PMID:22937162 includes direct characterization of the protein behavior under water-deficient conditions and its abundant expression pattern consistent with a desiccation protection role. Supporting Evidence: PMID:22937162 proteins in both families changed their conformation to an alpha-helical structure in water-deficient conditions as LEA proteins do PMID:22937162 suggesting their roles as molecular shield in water-deficient condition PMID:27649274 These abundantly expressed proteins included previously identified tardigrade-unique heat-soluble proteins, CAHS and SAHS, both of which maintain solubility even after heat treatment and are proposed to be involved in the protection of biomolecules during desiccation

📚 Additional Documentation

Deep Research Falcon

(SAHS2-deep-research-falcon.md)

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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: J7MAN2
Protein Description: RecName: Full=Secretory-abundant heat soluble protein 2 {ECO:0000303|PubMed:22937162}; Short=SAHS2 {ECO:0000303|PubMed:22937162}; AltName: Full=Tardigrade-specific intrinsically disordered protein SAHS2 {ECO:0000305}; Short=TDP SAHS2 {ECO:0000305}; Flags: Precursor;
Gene Information: Name=SAHS2 {ECO:0000303|PubMed:22937162}; ORFNames=RvY_02431;
Organism (full): Ramazzottius varieornatus (Water bear) (Tardigrade).
Protein Family: Belongs to the Secretory-abundant heat soluble protein
Key Domains: Calycin. (IPR012674)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "SAHS2" matches the protein description above
Verify the organism is correct: Ramazzottius varieornatus (Water bear) (Tardigrade).
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'SAHS2' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene SAHS2 (gene ID: SAHS2, UniProt: J7MAN2) in RAMVA.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Output

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: J7MAN2
Protein Description: RecName: Full=Secretory-abundant heat soluble protein 2 {ECO:0000303|PubMed:22937162}; Short=SAHS2 {ECO:0000303|PubMed:22937162}; AltName: Full=Tardigrade-specific intrinsically disordered protein SAHS2 {ECO:0000305}; Short=TDP SAHS2 {ECO:0000305}; Flags: Precursor;
Gene Information: Name=SAHS2 {ECO:0000303|PubMed:22937162}; ORFNames=RvY_02431;
Organism (full): Ramazzottius varieornatus (Water bear) (Tardigrade).
Protein Family: Belongs to the Secretory-abundant heat soluble protein
Key Domains: Calycin. (IPR012674)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "SAHS2" matches the protein description above
Verify the organism is correct: Ramazzottius varieornatus (Water bear) (Tardigrade).
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Please provide a comprehensive research report on the gene SAHS2 (gene ID: SAHS2, UniProt: J7MAN2) in RAMVA.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Research report: Functional annotation of SAHS2 (UniProt J7MAN2) from Ramazzottius varieornatus

0) Target verification (gene/protein identity)

The target protein is SAHS2 from the tardigrade Ramazzottius varieornatus, originally defined as part of the SAHS (Secretory Abundant Heat Soluble) family discovered by heat‑soluble proteomics in R. varieornatus (Yamaguchi et al., 2012-08-22, PLoS ONE, https://doi.org/10.1371/journal.pone.0044209). In that defining work, SAHS1 and SAHS2 are explicitly classified as “secretory” proteins (i.e., the “secretory abundant heat soluble” family), and SAHS2 is reported to have a four‑exon gene structure. (yamaguchi2012twonovelheatsoluble pages 3-5, yamaguchi2012twonovelheatsoluble pages 6-7)

Critical scope note: direct experimental assays in the retrieved literature are largely performed on other R. varieornatus SAHS paralogs (e.g., SAHS1/4/6) rather than SAHS2. Therefore, SAHS2 functional annotation below distinguishes (i) SAHS2-specific evidence (gene identity and gene structure; secretory prediction) from (ii) SAHS-family evidence used to infer likely SAHS2 role. (yamaguchi2012twonovelheatsoluble pages 3-5, yamaguchi2012twonovelheatsoluble pages 6-7, lim2024tardigradesecretoryproteins pages 3-5)

1) Key concepts and current understanding

1.1. What are SAHS proteins?

SAHS proteins are a tardigrade-specific family of abundant, heat‑soluble proteins identified by extracting proteins that remain soluble after heating (92°C for 15 min) and then identifying major bands by mass spectrometry and cDNA cloning. (yamaguchi2012twonovelheatsoluble pages 2-3)

SAHS proteins were defined as “secretory” based on N‑terminal signal peptides and subcellular localization analyses, in contrast to CAHS (cytoplasmic abundant heat soluble) proteins, which were assigned to cytosol/nucleus-associated protective roles. (yamaguchi2012twonovelheatsoluble pages 3-5, yamaguchi2012twonovelheatsoluble pages 5-6)

1.2. Stress biology concept: dehydration-driven structural plasticity

A core concept in tardigrade stress tolerance is that some tardigrade-specific proteins (including SAHS) exhibit secondary-structure changes under water-deficient / desolvating conditions, analogous to LEA-like “molecular shield” models.

In the defining SAHS/CAHS work, SAHS proteins are described as β-structure-rich in hydrated conditions (demonstrated for SAHS1 by CD) but converting toward α-helical conformations in water-deficient conditions (family-level statement; SAHS1 requires strong desolvation mimic conditions such as >50% TFE to show α-helical conversion). (yamaguchi2012twonovelheatsoluble pages 5-6, yamaguchi2012twonovelheatsoluble pages 3-5)

2) SAHS2: likely molecular function and mechanism (evidence-weighted)

2.1. Primary inferred function: extracellular/membrane-associated desiccation protection

Family-level functional assays (2024) strongly support that secreted SAHS proteins act as extracellular protectants of membrane-containing structures, rather than general enzyme stabilizers:

Liposome protection: In POPC liposome drying/rehydration assays, desiccation causes substantial liposome fusion/aggregation (appearance of large particles; loss of initial ~50–100 nm population). Addition of SAHS proteins (tested SAHS paralogs include R. varieornatus SAHS1/4/6 and a Hypsibius SAHS) at 0.1–10 mg/mL partially to strongly preserves small size distributions and suppresses formation of large fused particles; effects exceeded BSA controls and were comparable to trehalose in some conditions. (lim2024tardigradesecretoryproteins pages 3-5, lim2024tardigradesecretoryproteins media f52027ea)
Microbial survival: Extracellular application of SAHS proteins during drying improves survival of two bacteria (E. coli and Rhizobium tropici) after 48 h desiccation. The text reports >10-fold survival enhancement for E. coli in some conditions and summarizes performance as substantially better than BSA and (in some assays) better than trehalose. (lim2024tardigradesecretoryproteins pages 3-5, lim2024tardigradesecretoryproteins pages 6-7, lim2024tardigradesecretoryproteins media b0bc6f49)
Negative/limited enzyme protection: In the same study, SAHS proteins did not substantially outperform BSA in protecting lactate dehydrogenase activity after desiccation/rehydration, supporting specialization toward membranes/cells rather than broad enzyme chaperoning. (lim2024tardigradesecretoryproteins pages 7-8, lim2024tardigradesecretoryproteins pages 6-7)

Implication for SAHS2: Since SAHS2 is a canonical SAHS-family member in R. varieornatus and is predicted secretory like SAHS1, it is most parsimonious that SAHS2 contributes to extracellular stabilization (especially of membranes or secreted/extracellular structures) during desiccation, though direct SAHS2-specific assays were not found in the retrieved corpus. (yamaguchi2012twonovelheatsoluble pages 3-5, lim2024tardigradesecretoryproteins pages 3-5)

2.2. Proposed mechanism: dehydration-driven conformational change and higher-order assemblies

Lim et al. (2024-05, Communications Biology, https://doi.org/10.1038/s42003-024-06336-w) combine structural comparisons, AlphaFold-assisted analysis, and MD simulations to propose that SAHS proteins have fatty-acid-binding-protein (FABP)-like β-barrel folds with large internal cavities, and that loss of cavity solvent during desiccation destabilizes β-structure, promoting conformational rearrangements and potentially gel-/network-like assemblies that stabilize membranes and extracellular structures. (lim2024tardigradesecretoryproteins pages 1-3, lim2024tardigradesecretoryproteins pages 6-7)

This mechanistic model is consistent with the earlier observation that SAHS proteins can undergo β→α secondary-structure shifts under desolvating conditions. (yamaguchi2012twonovelheatsoluble pages 3-5, lim2024tardigradesecretoryproteins pages 6-7)

3) Cellular and organismal context: expression and localization

3.1. Secretory nature (signal peptide; secretion)

In the original SAHS-family description, SAHS1 and SAHS2 were predicted secretory (signal peptides), and SAHS1-GFP experiments supported secretion into culture media in heterologous systems, motivating the idea that SAHS proteins protect extracellular components. (yamaguchi2012twonovelheatsoluble pages 3-5, yamaguchi2012twonovelheatsoluble pages 5-6)

3.2. Tissue/cell specificity in R. varieornatus (major 2023 advance)

Tanaka et al. (2023-01, PNAS, https://doi.org/10.1073/pnas.2216739120) developed TardiVec, an in vivo expression system using R. varieornatus regulatory regions, enabling tissue-specific live imaging.

Using a SAHS promoter (pRvSAHS1), they found SAHS-family expression is strongly enriched in “storage cells” (free-floating cells in the body cavity). RNA-seq supported that SAHS-family transcripts are ~5–20× higher in storage cells compared with whole-body measurements, indicating specialized expression of SAHS proteins in that cell type in natural settings. (tanaka2023invivoexpression pages 3-4)

They further observed SAHS1 fusion protein localizing to vesicle-like structures within storage cells, and in some cases appearing in the body cavity, leading to the interpretation that SAHS proteins are synthesized in storage cells and can be secreted/transported to protect other tissues during anhydrobiosis. (tanaka2023invivoexpression pages 6-7, tanaka2023invivoexpression pages 4-6)

Implication for SAHS2: While SAHS2 is not individually reported in these TardiVec excerpts, SAHS2 is part of the SAHS gene family; thus SAHS2 is likely expressed in or coordinated with storage-cell secretory programs and may function in the body cavity/extracellular milieu. (tanaka2023invivoexpression pages 3-4, yamaguchi2012twonovelheatsoluble pages 3-5)

4) Evolutionary and comparative context (expert analysis from authoritative sources)

4.1. Tardigrade-specific innovation

The SAHS family was originally reported as conserved among tardigrades and not found in other phyla, implying lineage-specific innovation associated with anhydrobiosis. (yamaguchi2012twonovelheatsoluble pages 1-2)

4.2. Gene family dynamics (2024 phylogenomic synthesis)

A 2024 phylogenomic analysis of desiccation/temperature-related families in tardigrades reconstructed phylogenies for multiple extremotolerance-linked families, including SAHS, and inferred numerous independent gene duplications across these families, consistent with complex and repeated evolutionary adaptation to aridity in limnoterrestrial environments. (Fleming et al., 2024, Genome Biology and Evolution, https://doi.org/10.1093/gbe/evad217) (lim2024tardigradesecretoryproteins pages 1-3)

5) Applications and real-world implementations (2024 focus)

The strongest evidence for real-world application comes from direct demonstration that extracellular SAHS proteins can stabilize microbes during drying, including Rhizobium tropici, a bacterium relevant to plant-associated contexts. The authors explicitly frame this as a potential route to cell preservation and microbial stabilization (e.g., to improve survivability during desiccation-based storage/handling), and also demonstrate protection of membrane structures (liposomes), suggesting broader biostabilization uses for membrane-bound biological materials. (lim2024tardigradesecretoryproteins pages 1-3, lim2024tardigradesecretoryproteins pages 8-9, lim2024tardigradesecretoryproteins media b0bc6f49)

6) Quantitative highlights (recent studies prioritized)

Storage-cell enrichment: SAHS-family transcripts are enriched ~5–20× in storage cells vs whole body (TardiVec RNA-seq), and the SAHS promoter drives storage-cell-specific expression. (Tanaka et al., 2023-01, PNAS, https://doi.org/10.1073/pnas.2216739120) (tanaka2023invivoexpression pages 3-4)
Liposome stabilization: Drying causes major liposome fusion/aggregation; SAHS proteins at mg/mL levels preserve small size populations and suppress large particles compared to controls (DLS; Lim et al., 2024-05). (lim2024tardigradesecretoryproteins pages 3-5, lim2024tardigradesecretoryproteins media f52027ea)
Microbial desiccation survival: SAHS proteins improve E. coli and R. tropici survival after 48 h drying; the study reports >10-fold survival enhancement in some conditions and summarizes SAHS as strongly outperforming BSA and in some assays outperforming trehalose. (Lim et al., 2024-05) (lim2024tardigradesecretoryproteins pages 3-5, lim2024tardigradesecretoryproteins pages 6-7, lim2024tardigradesecretoryproteins media b0bc6f49)

7) Practical functional annotation summary for SAHS2 (UniProt J7MAN2)

Recommended primary annotation (most supported):
* Molecular role: secreted, heat-soluble stress protein likely functioning as an extracellular protectant during desiccation/anhydrobiosis, with strongest evidence for membrane/membrane-structure stabilization rather than broad enzyme chaperoning. (yamaguchi2012twonovelheatsoluble pages 3-5, lim2024tardigradesecretoryproteins pages 6-7)
* Biological process: anhydrobiosis/desiccation tolerance; extracellular stabilization during dehydration and rehydration. (yamaguchi2012twonovelheatsoluble pages 1-2, lim2024tardigradesecretoryproteins pages 3-5)
* Cellular localization: secretory pathway / extracellular space (signal peptide; secretion inferred for SAHS family; in vivo expression suggests origin in storage cells and potential release into body cavity). (yamaguchi2012twonovelheatsoluble pages 3-5, tanaka2023invivoexpression pages 3-4)
* Mechanistic hypothesis: dehydration-driven destabilization of β-structure and/or cavity desolvation leads to conformational changes and higher-order assemblies that stabilize membranes and extracellular structures. (lim2024tardigradesecretoryproteins pages 6-7)

Evidence limitations (SAHS2-specific):
Direct biochemical/functional characterization in the retrieved sources is primarily for SAHS1 and other SAHS paralogs; SAHS2-specific evidence is strongest for its membership in the secretory SAHS family and gene structure (four exons) rather than direct assay results. (yamaguchi2012twonovelheatsoluble pages 6-7, lim2024tardigradesecretoryproteins pages 3-5)

Evidence summary table

Aspect	Key findings (with numbers)	Evidence type (experiment/bioinformatics)	Primary source (authors year journal)	URL/DOI	Notes on SAHS2-specific vs family-level
Gene/protein identity	SAHS2 in Ramazzottius varieornatus is part of the SAHS = Secretory Abundant Heat Soluble family; defining study states SAHS1 and SAHS2 are secretory, and SAHS2 has 4 exons. SAHS proteins were identified among major heat-soluble proteins after heating extracts to 92°C for 15 min and analyzing heat-soluble fractions by MS/RACE (yamaguchi2012twonovelheatsoluble pages 2-3, yamaguchi2012twonovelheatsoluble pages 6-7, yamaguchi2012twonovelheatsoluble pages 3-5)	Proteomics, gene structure, localization prediction	Yamaguchi et al. 2012, PLoS ONE	https://doi.org/10.1371/journal.pone.0044209	Directly relevant to SAHS2 identity; strongest SAHS2-specific evidence is family membership, secretory prediction, and exon structure rather than direct biochemical assay (yamaguchi2012twonovelheatsoluble pages 6-7, yamaguchi2012twonovelheatsoluble pages 3-5)
Localization: signal peptide and secretion	SAHS proteins contain N-terminal secretory signal peptides; TargetP/SignalP predicted SAHS1 and SAHS2 as secretory. SAHS1-GFP was detected in culture medium, supporting secretion; authors inferred SAHS proteins protect extracellular components/secretory organelles (yamaguchi2012twonovelheatsoluble pages 3-5, yamaguchi2012twonovelheatsoluble pages 5-6)	Bioinformatics plus heterologous expression/immunoblot	Yamaguchi et al. 2012, PLoS ONE	https://doi.org/10.1371/journal.pone.0044209	SAHS2 secretion is predicted, not directly shown; direct secretion experiment was for SAHS1 (yamaguchi2012twonovelheatsoluble pages 3-5, yamaguchi2012twonovelheatsoluble pages 5-6)
Localization: tissue/cell specificity	In vivo TardiVec work showed SAHS-family promoter activity is highly enriched in storage cells; pRvSAHS1 drove strong expression in free-floating storage cells, and SAHS1-mEGFP localized to vesicle-like structures in storage cells and sometimes body cavity. RNA-seq showed SAHS transcripts enriched about ~5–20× in storage cells vs whole body (tanaka2023invivoexpression pages 3-4, tanaka2023invivoexpression pages 4-6, tanaka2023invivoexpression pages 2-3)	In vivo transgenesis, live imaging, RNA-seq	Tanaka et al. 2023, PNAS	https://doi.org/10.1073/pnas.2216739120	This is SAHS1/promoter-family evidence, not SAHS2-specific; useful for likely native context of SAHS2 as a secreted storage-cell-associated protectant (tanaka2023invivoexpression pages 6-7, tanaka2023invivoexpression pages 3-4)
Structural/domain info	Early work found SAHS proteins are beta-structure-rich in hydrated conditions and shift toward alpha-helix under water-deficient/desolvating conditions; SAHS1 had CD minimum at 215 nm and required >50% TFE for alpha-helical conversion. Later work describes SAHS proteins as FABP-like/calycin-like beta-barrels with large internal cavities and structures solved for RvSAHS1/4; 2024 analyses propose dehydration-induced cavity solvent loss destabilizes the beta-barrel and promotes alternative protective conformations/networks (yamaguchi2012twonovelheatsoluble pages 5-6, lim2024tardigradesecretoryproteins pages 7-8, lim2024tardigradesecretoryproteins pages 6-7, roseteenriquez2025survivingdesiccationkey pages 13-15, yamaguchi2012twonovelheatsoluble pages 3-5)	CD spectroscopy, structural biology, MD simulation, comparative modeling	Yamaguchi et al. 2012, PLoS ONE; Lim et al. 2024, Communications Biology	https://doi.org/10.1371/journal.pone.0044209; https://doi.org/10.1038/s42003-024-06336-w	No direct SAHS2 structure in cited evidence; inference is family-level. UniProt/J7MAN2 annotation of calycin is consistent with later family-level FABP-like beta-barrel evidence (lim2024tardigradesecretoryproteins pages 7-8, lim2024tardigradesecretoryproteins pages 6-7)
Functional assay: membrane/liposome protection	Drying/rehydration of POPC liposomes caused major fusion/aggregation: initial diameters ~50–100 nm, but after drying <10% remained in that range and large particles around ~360 and 4000 nm formed. With SAHS proteins at 10, 1, or 0.1 mg/mL, major peaks stayed near ~60–100 nm and no particles >200 nm were observed; performance exceeded BSA and was comparable to trehalose at 10 mg/mL (lim2024tardigradesecretoryproteins pages 1-3, lim2024tardigradesecretoryproteins pages 3-5, lim2024tardigradesecretoryproteins pages 6-7, lim2024tardigradesecretoryproteins media f52027ea)	In vitro DLS liposome assay	Lim et al. 2024, Communications Biology	https://doi.org/10.1038/s42003-024-06336-w	Assayed proteins included RvSAHS1/4/6 and HeSAHS4, not SAHS2 specifically; supports extracellular membrane-protection role for SAHS family that may extend to SAHS2 (lim2024tardigradesecretoryproteins pages 3-5, lim2024tardigradesecretoryproteins media f52027ea)
Functional assay: microbial desiccation protection	Extracellular addition of SAHS proteins improved microbial survival after 48 h drying. For E. coli, 0.5 mg/mL RvSAHS1 gave >10-fold survival enhancement; across assays SAHS proteins gave roughly ~50-fold improvement overall, at least ~10-fold better than BSA and ~3-fold better than trehalose. A single SAHS protein also stabilized Rhizobium tropici (lim2024tardigradesecretoryproteins pages 3-5, lim2024tardigradesecretoryproteins pages 8-9, lim2024tardigradesecretoryproteins pages 6-7, lim2024tardigradesecretoryproteins media b0bc6f49)	Desiccation survival/CFU assays	Lim et al. 2024, Communications Biology	https://doi.org/10.1038/s42003-024-06336-w	Family-level evidence only; SAHS2 not individually tested in the cited excerpts (lim2024tardigradesecretoryproteins pages 8-9, lim2024tardigradesecretoryproteins media b0bc6f49)
Functional assay: enzyme protection	SAHS proteins did not significantly outperform BSA in protecting lactate dehydrogenase (LDH) after desiccation/rehydration; only slight protection was observed, indicating SAHS may preferentially protect membranes/cells rather than soluble enzymes (lim2024tardigradesecretoryproteins pages 8-9, lim2024tardigradesecretoryproteins pages 7-8, lim2024tardigradesecretoryproteins pages 6-7)	Enzyme activity assay	Lim et al. 2024, Communications Biology	https://doi.org/10.1038/s42003-024-06336-w	Negative/limited family-level result; no SAHS2-specific enzyme assay in cited evidence
Evolutionary context	SAHS proteins are tardigrade-specific and not found outside the phylum in the original study; homologs were found across tardigrades, with abundant expression in Hypsibius dujardini ESTs (100 ESTs for SAHS vs 15 for actin and 64 for EF1a). A 2024 phylogenomic study found complex histories with multiple independent duplications of SAHS family genes in tardigrades; R. varieornatus and related taxa show SAHS diversification linked to extremotolerance evolution (yamaguchi2012twonovelheatsoluble pages 1-2, yamaguchi2012twonovelheatsoluble pages 3-5)	Comparative genomics, transcriptomics, phylogenomics	Yamaguchi et al. 2012, PLoS ONE; Fleming et al. 2024, Genome Biology and Evolution	https://doi.org/10.1371/journal.pone.0044209; https://doi.org/10.1093/gbe/evad217	SAHS2 is one member of a broader duplicated family; evolutionary conclusions are family-level rather than gene-specific
Comparative genomics in R. varieornatus	Comparative genome analysis reported that no SAHS2 ortholog was found in Hypsibius dujardini, emphasizing lineage-specific expansion/retention in R. varieornatus and related anhydrobiotic lineages (from retrieved snippet)	Comparative genomics	Yoshida et al. 2017, PLOS Biology	https://doi.org/10.1371/journal.pbio.2002266	Supports distinct SAHS2 evolutionary trajectory; evidence is orthology-level rather than direct function
Key quantitative data points for annotation	92°C for 15 min heat-solubility screen; SAHS2 gene has 4 exons; SAHS-family transcripts enriched ~5–20× in storage cells; hydrated SAHS1 CD minimum at 215 nm and alpha-helical conversion above >50% TFE; liposomes initially ~50–100 nm, dried samples produced ~360 and 4000 nm aggregates, but SAHS-treated samples retained ~60–100 nm peaks with no particles >200 nm; E. coli survival improved >10-fold with 0.5 mg/mL RvSAHS1, with some assays showing ~50-fold gains overall after 48 h drying (yamaguchi2012twonovelheatsoluble pages 2-3, yamaguchi2012twonovelheatsoluble pages 6-7, lim2024tardigradesecretoryproteins pages 3-5, lim2024tardigradesecretoryproteins pages 6-7, lim2024tardigradesecretoryproteins media f52027ea, tanaka2023invivoexpression pages 3-4)	Mixed: proteomics, gene structure, imaging, CD, DLS, CFU assays	Yamaguchi et al. 2012, Tanaka et al. 2023, Lim et al. 2024	https://doi.org/10.1371/journal.pone.0044209; https://doi.org/10.1073/pnas.2216739120; https://doi.org/10.1038/s42003-024-06336-w	Most numeric values are family-level or SAHS1-centered; direct SAHS2-specific numbers remain sparse, so functional annotation should distinguish direct evidence from family inference

Table: This table compiles the strongest available evidence for functional annotation of SAHS2 (UniProt J7MAN2) in Ramazzottius varieornatus, separating SAHS2-specific findings from broader SAHS family-level inference. It is useful for assigning likely localization, structural class, and protective role while being explicit about evidentiary limits.

Key figures supporting quantitative claims (Lim et al., 2024)

The following extracted figure crops contain the quantitative DLS liposome distributions and microbial survival plots referenced above. (lim2024tardigradesecretoryproteins media f52027ea, lim2024tardigradesecretoryproteins media b0bc6f49)

References (URLs and publication dates)

Yamaguchi A. et al. Two Novel Heat-Soluble Protein Families Abundantly Expressed in an Anhydrobiotic Tardigrade. PLoS ONE (2012-08-22). https://doi.org/10.1371/journal.pone.0044209 (yamaguchi2012twonovelheatsoluble pages 2-3, yamaguchi2012twonovelheatsoluble pages 6-7)
Tanaka S. et al. In vivo expression vector derived from anhydrobiotic tardigrade genome enables live imaging in Eutardigrada. PNAS (2023-01). https://doi.org/10.1073/pnas.2216739120 (tanaka2023invivoexpression pages 3-4, tanaka2023invivoexpression pages 4-6)
Lim S. et al. Tardigrade secretory proteins protect biological structures from desiccation. Communications Biology (2024-05). https://doi.org/10.1038/s42003-024-06336-w (lim2024tardigradesecretoryproteins pages 3-5, lim2024tardigradesecretoryproteins pages 6-7)
Fleming JF. et al. The Evolution of Temperature and Desiccation-Related Protein Families in Tardigrada Reveals a Complex Acquisition of Extremotolerance. Genome Biology and Evolution (2024; metadata in retrieval indicates Nov 2024). https://doi.org/10.1093/gbe/evad217 (lim2024tardigradesecretoryproteins pages 1-3)

References

(yamaguchi2012twonovelheatsoluble pages 3-5): Ayami Yamaguchi, Sae Tanaka, Shiho Yamaguchi, Hirokazu Kuwahara, Chizuko Takamura, Shinobu Imajoh-Ohmi, Daiki D. Horikawa, Atsushi Toyoda, Toshiaki Katayama, Kazuharu Arakawa, Asao Fujiyama, Takeo Kubo, and Takekazu Kunieda. Two novel heat-soluble protein families abundantly expressed in an anhydrobiotic tardigrade. PLoS ONE, 7:e44209, Aug 2012. URL: https://doi.org/10.1371/journal.pone.0044209, doi:10.1371/journal.pone.0044209. This article has 195 citations and is from a peer-reviewed journal.
(yamaguchi2012twonovelheatsoluble pages 6-7): Ayami Yamaguchi, Sae Tanaka, Shiho Yamaguchi, Hirokazu Kuwahara, Chizuko Takamura, Shinobu Imajoh-Ohmi, Daiki D. Horikawa, Atsushi Toyoda, Toshiaki Katayama, Kazuharu Arakawa, Asao Fujiyama, Takeo Kubo, and Takekazu Kunieda. Two novel heat-soluble protein families abundantly expressed in an anhydrobiotic tardigrade. PLoS ONE, 7:e44209, Aug 2012. URL: https://doi.org/10.1371/journal.pone.0044209, doi:10.1371/journal.pone.0044209. This article has 195 citations and is from a peer-reviewed journal.
(lim2024tardigradesecretoryproteins pages 3-5): Samuel Lim, Charles B. Reilly, Zeina Barghouti, Benedetto Marelli, Jeffrey C. Way, and Pamela A. Silver. Tardigrade secretory proteins protect biological structures from desiccation. Communications Biology, May 2024. URL: https://doi.org/10.1038/s42003-024-06336-w, doi:10.1038/s42003-024-06336-w. This article has 17 citations and is from a peer-reviewed journal.
(yamaguchi2012twonovelheatsoluble pages 2-3): Ayami Yamaguchi, Sae Tanaka, Shiho Yamaguchi, Hirokazu Kuwahara, Chizuko Takamura, Shinobu Imajoh-Ohmi, Daiki D. Horikawa, Atsushi Toyoda, Toshiaki Katayama, Kazuharu Arakawa, Asao Fujiyama, Takeo Kubo, and Takekazu Kunieda. Two novel heat-soluble protein families abundantly expressed in an anhydrobiotic tardigrade. PLoS ONE, 7:e44209, Aug 2012. URL: https://doi.org/10.1371/journal.pone.0044209, doi:10.1371/journal.pone.0044209. This article has 195 citations and is from a peer-reviewed journal.
(yamaguchi2012twonovelheatsoluble pages 5-6): Ayami Yamaguchi, Sae Tanaka, Shiho Yamaguchi, Hirokazu Kuwahara, Chizuko Takamura, Shinobu Imajoh-Ohmi, Daiki D. Horikawa, Atsushi Toyoda, Toshiaki Katayama, Kazuharu Arakawa, Asao Fujiyama, Takeo Kubo, and Takekazu Kunieda. Two novel heat-soluble protein families abundantly expressed in an anhydrobiotic tardigrade. PLoS ONE, 7:e44209, Aug 2012. URL: https://doi.org/10.1371/journal.pone.0044209, doi:10.1371/journal.pone.0044209. This article has 195 citations and is from a peer-reviewed journal.
(lim2024tardigradesecretoryproteins media f52027ea): Samuel Lim, Charles B. Reilly, Zeina Barghouti, Benedetto Marelli, Jeffrey C. Way, and Pamela A. Silver. Tardigrade secretory proteins protect biological structures from desiccation. Communications Biology, May 2024. URL: https://doi.org/10.1038/s42003-024-06336-w, doi:10.1038/s42003-024-06336-w. This article has 17 citations and is from a peer-reviewed journal.
(lim2024tardigradesecretoryproteins pages 6-7): Samuel Lim, Charles B. Reilly, Zeina Barghouti, Benedetto Marelli, Jeffrey C. Way, and Pamela A. Silver. Tardigrade secretory proteins protect biological structures from desiccation. Communications Biology, May 2024. URL: https://doi.org/10.1038/s42003-024-06336-w, doi:10.1038/s42003-024-06336-w. This article has 17 citations and is from a peer-reviewed journal.
(lim2024tardigradesecretoryproteins media b0bc6f49): Samuel Lim, Charles B. Reilly, Zeina Barghouti, Benedetto Marelli, Jeffrey C. Way, and Pamela A. Silver. Tardigrade secretory proteins protect biological structures from desiccation. Communications Biology, May 2024. URL: https://doi.org/10.1038/s42003-024-06336-w, doi:10.1038/s42003-024-06336-w. This article has 17 citations and is from a peer-reviewed journal.
(lim2024tardigradesecretoryproteins pages 7-8): Samuel Lim, Charles B. Reilly, Zeina Barghouti, Benedetto Marelli, Jeffrey C. Way, and Pamela A. Silver. Tardigrade secretory proteins protect biological structures from desiccation. Communications Biology, May 2024. URL: https://doi.org/10.1038/s42003-024-06336-w, doi:10.1038/s42003-024-06336-w. This article has 17 citations and is from a peer-reviewed journal.
(lim2024tardigradesecretoryproteins pages 1-3): Samuel Lim, Charles B. Reilly, Zeina Barghouti, Benedetto Marelli, Jeffrey C. Way, and Pamela A. Silver. Tardigrade secretory proteins protect biological structures from desiccation. Communications Biology, May 2024. URL: https://doi.org/10.1038/s42003-024-06336-w, doi:10.1038/s42003-024-06336-w. This article has 17 citations and is from a peer-reviewed journal.
(tanaka2023invivoexpression pages 3-4): Sae Tanaka, Kazuhiro Aoki, and Kazuharu Arakawa. In vivo expression vector derived from anhydrobiotic tardigrade genome enables live imaging in eutardigrada. Proceedings of the National Academy of Sciences, Jan 2023. URL: https://doi.org/10.1073/pnas.2216739120, doi:10.1073/pnas.2216739120. This article has 27 citations and is from a highest quality peer-reviewed journal.
(tanaka2023invivoexpression pages 6-7): Sae Tanaka, Kazuhiro Aoki, and Kazuharu Arakawa. In vivo expression vector derived from anhydrobiotic tardigrade genome enables live imaging in eutardigrada. Proceedings of the National Academy of Sciences, Jan 2023. URL: https://doi.org/10.1073/pnas.2216739120, doi:10.1073/pnas.2216739120. This article has 27 citations and is from a highest quality peer-reviewed journal.
(tanaka2023invivoexpression pages 4-6): Sae Tanaka, Kazuhiro Aoki, and Kazuharu Arakawa. In vivo expression vector derived from anhydrobiotic tardigrade genome enables live imaging in eutardigrada. Proceedings of the National Academy of Sciences, Jan 2023. URL: https://doi.org/10.1073/pnas.2216739120, doi:10.1073/pnas.2216739120. This article has 27 citations and is from a highest quality peer-reviewed journal.
(yamaguchi2012twonovelheatsoluble pages 1-2): Ayami Yamaguchi, Sae Tanaka, Shiho Yamaguchi, Hirokazu Kuwahara, Chizuko Takamura, Shinobu Imajoh-Ohmi, Daiki D. Horikawa, Atsushi Toyoda, Toshiaki Katayama, Kazuharu Arakawa, Asao Fujiyama, Takeo Kubo, and Takekazu Kunieda. Two novel heat-soluble protein families abundantly expressed in an anhydrobiotic tardigrade. PLoS ONE, 7:e44209, Aug 2012. URL: https://doi.org/10.1371/journal.pone.0044209, doi:10.1371/journal.pone.0044209. This article has 195 citations and is from a peer-reviewed journal.
(lim2024tardigradesecretoryproteins pages 8-9): Samuel Lim, Charles B. Reilly, Zeina Barghouti, Benedetto Marelli, Jeffrey C. Way, and Pamela A. Silver. Tardigrade secretory proteins protect biological structures from desiccation. Communications Biology, May 2024. URL: https://doi.org/10.1038/s42003-024-06336-w, doi:10.1038/s42003-024-06336-w. This article has 17 citations and is from a peer-reviewed journal.
(tanaka2023invivoexpression pages 2-3): Sae Tanaka, Kazuhiro Aoki, and Kazuharu Arakawa. In vivo expression vector derived from anhydrobiotic tardigrade genome enables live imaging in eutardigrada. Proceedings of the National Academy of Sciences, Jan 2023. URL: https://doi.org/10.1073/pnas.2216739120, doi:10.1073/pnas.2216739120. This article has 27 citations and is from a highest quality peer-reviewed journal.
(roseteenriquez2025survivingdesiccationkey pages 13-15): María Rosete-Enríquez, Victor Rivelino Juárez-González, Esmeralda Escobar-Muciño, Jesús Muñoz-Rojas, and Verónica Quintero-Hernández. Surviving desiccation: key factors underlying tolerance in prokaryotes and eukaryotes. Protoplasma, Nov 2025. URL: https://doi.org/10.1007/s00709-025-02134-1, doi:10.1007/s00709-025-02134-1. This article has 2 citations and is from a peer-reviewed journal.

Citations

yamaguchi2012twonovelheatsoluble pages 2-3
tanaka2023invivoexpression pages 3-4
yamaguchi2012twonovelheatsoluble pages 1-2
lim2024tardigradesecretoryproteins pages 1-3
lim2024tardigradesecretoryproteins pages 6-7
yamaguchi2012twonovelheatsoluble pages 3-5
yamaguchi2012twonovelheatsoluble pages 6-7
lim2024tardigradesecretoryproteins pages 3-5
yamaguchi2012twonovelheatsoluble pages 5-6
lim2024tardigradesecretoryproteins pages 7-8
tanaka2023invivoexpression pages 6-7
tanaka2023invivoexpression pages 4-6
lim2024tardigradesecretoryproteins pages 8-9
tanaka2023invivoexpression pages 2-3
roseteenriquez2025survivingdesiccationkey pages 13-15
https://doi.org/10.1371/journal.pone.0044209
https://doi.org/10.1038/s42003-024-06336-w
https://doi.org/10.1073/pnas.2216739120
https://doi.org/10.1093/gbe/evad217
https://doi.org/10.1371/journal.pone.0044209;
https://doi.org/10.1371/journal.pbio.2002266
https://doi.org/10.1073/pnas.2216739120;
https://doi.org/10.1371/journal.pone.0044209,
https://doi.org/10.1038/s42003-024-06336-w,
https://doi.org/10.1073/pnas.2216739120,
https://doi.org/10.1007/s00709-025-02134-1,

📄 View Raw YAML

id: J7MAN2
gene_symbol: SAHS2
product_type: PROTEIN
status: IN_PROGRESS
taxon:
  id: NCBITaxon:947166
  label: Ramazzottius varieornatus
description: >-
  Secretory-abundant heat soluble protein 2 (SAHS2) is a tardigrade-specific secreted protein
  belonging to the SAHS family, which adopts a beta-barrel fold structurally similar to fatty
  acid-binding proteins (FABPs). SAHS proteins are abundantly expressed, heat-soluble, and are
  proposed to act as molecular shields that protect extracellular components during desiccation
  (anhydrobiosis). SAHS2 has a signal peptide (residues 1-19), three conserved SAHS domains
  (SAHS-c1, c2, c3), and an N-linked glycosylation site. The SAHS family is unique to
  tardigrades and has no homologs outside Tardigrada, except for distant structural similarity
  to metazoan FABPs. Crystal structures of the paralog SAHS1 (RvSAHS1) revealed two putative
  ligand binding sites where fatty acids can bind (PMID:28703282), establishing SAHS proteins
  as a new FABP-like family. SAHS2 is one of 13 SAHS paralogs encoded in the R. varieornatus
  genome and is constitutively and abundantly expressed (PMID:27649274).
existing_annotations:
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: >-
      SAHS2 is annotated to the extracellular region based on IEA mapping from UniProtKB
      subcellular location vocabulary. UniProt marks SAHS2 as "Secreted" based on similarity
      to SAHS1 (J7MFT5). The protein has a predicted signal peptide (residues 1-19) and was
      originally identified in the heat-soluble proteome of tardigrades (PMID:22937162).
      SAHS proteins are described as having a secretory localization distinct from the
      cytoplasmic CAHS family (PMID:22937162). The annotation to GO:0005576 extracellular
      region is well supported.
    action: ACCEPT
    reason: >-
      SAHS2 has a signal peptide and is described as a secretory protein. The original
      proteomics study identified SAHS proteins as having distinct subcellular localization
      from CAHS proteins, with SAHS being secretory (PMID:22937162). The name itself
      (Secretory Abundant Heat Soluble) reflects this localization. Extracellular region is
      the appropriate GO CC term for a secreted protein.
    supported_by:
      - reference_id: PMID:22937162
        supporting_text: >-
          We named them Cytoplasmic Abundant Heat Soluble (CAHS) and Secretory Abundant
          Heat Soluble (SAHS) protein families, according to their localization.
      - reference_id: PMID:28703282
        supporting_text: >-
          Secretory abundant heat-soluble (SAHS) proteins have been reported as candidates
          for anhydrobiosis-related proteins in tardigrades, which seem to protect
          extracellular components and/or secretory organelles.
- term:
    id: GO:0008289
    label: lipid binding
  evidence_type: ISS
  original_reference_id: PMID:28703282
  review:
    summary: >-
      SAHS2 is not currently annotated with lipid binding in GOA, but structural studies of
      the paralog SAHS1 (RvSAHS1) demonstrate that SAHS proteins adopt a beta-barrel fold
      homologous to fatty acid-binding proteins (FABPs) with two putative ligand binding sites
      (PMID:28703282). CDD classifies SAHS2 as containing an FABP domain (cd00742), InterPro
      assigns calycin fold (IPR012674), and SUPFAM classifies it in the Lipocalin superfamily
      (SSF50814). Crystal structure of SAHS4 showed variant binding preferences at these sites
      (PMID:29493034), suggesting functional diversification within the SAHS family.
    action: NEW
    reason: >-
      Although no direct lipid binding assay has been performed on SAHS2 specifically, the
      structural evidence from the SAHS1 crystal structure (PMID:28703282) combined with the
      FABP domain classification (CDD cd00742) and calycin/lipocalin superfamily membership
      strongly supports lipid binding as a molecular function. SAHS1 (J7MFT5) already has an
      IEA lipid binding annotation via InterPro. The same structural basis applies to SAHS2,
      which shares the conserved SAHS domains and FABP-like fold. ISS evidence from the
      paralog SAHS1 crystal structure is appropriate.
    additional_reference_ids:
      - PMID:29493034
    supported_by:
      - reference_id: PMID:28703282
        supporting_text: >-
          RvSAHS1 shows a beta-barrel structure similar to fatty acid-binding proteins
          (FABPs), in which hydrophilic residues form peculiar hydrogen bond networks...
          We identified two putative ligand-binding sites: one that superimposes on those
          of some FABPs and the other, unique to and conserved in SAHS proteins. These
          results indicate that SAHS proteins constitute a new FABP family.
      - reference_id: PMID:29493034
        supporting_text: >-
          A previous crystallographic study revealed that a SAHS protein (RvSAHS1) from one
          of the toughest tardigrades, Ramazzottius varieornatus, has a beta-barrel
          architecture similar to fatty acid binding proteins (FABPs) and two putative
          ligand binding sites (LBS1 and LBS2) where fatty acids can bind.
- term:
    id: GO:0009269
    label: response to desiccation
  evidence_type: IDA
  original_reference_id: PMID:22937162
  review:
    summary: >-
      SAHS proteins were discovered through heat-soluble proteomics specifically aimed at
      identifying desiccation tolerance factors in tardigrades (PMID:22937162). SAHS2 changes
      conformation from beta-structure to alpha-helical structure under water-deficient
      conditions, similar to LEA proteins, suggesting a direct protective role during
      desiccation. The protein is constitutively and abundantly expressed, consistent with the
      fact that R. varieornatus tolerates rapid desiccation without significant transcriptional
      regulation (PMID:27649274). UniProt annotates SAHS2 as acting as a molecular shield in
      water-deficient conditions.
    action: NEW
    reason: >-
      Response to desiccation (GO:0009269) is a core biological process for SAHS2. The
      protein was identified specifically in the context of anhydrobiosis research, changes
      conformation under desiccating conditions, and is proposed to function as a molecular
      shield protecting extracellular components during desiccation. The evidence from
      PMID:22937162 includes direct characterization of the protein behavior under
      water-deficient conditions and its abundant expression pattern consistent with a
      desiccation protection role.
    additional_reference_ids:
      - PMID:27649274
    supported_by:
      - reference_id: PMID:22937162
        supporting_text: >-
          proteins in both families changed their conformation to an alpha-helical structure
          in water-deficient conditions as LEA proteins do
      - reference_id: PMID:22937162
        supporting_text: >-
          suggesting their roles as molecular shield in water-deficient condition
      - reference_id: PMID:27649274
        supporting_text: >-
          These abundantly expressed proteins included previously identified
          tardigrade-unique heat-soluble proteins, CAHS and SAHS, both of which maintain
          solubility even after heat treatment and are proposed to be involved in the
          protection of biomolecules during desiccation
references:
- id: GO_REF:0000044
  title: >-
    Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping, accompanied by conservative changes to GO terms applied by
    UniProt
  findings: []
- id: PMID:22937162
  title: >-
    Two novel heat-soluble protein families abundantly expressed in an anhydrobiotic
    tardigrade
  findings:
    - statement: >-
        SAHS proteins were identified via heat-soluble proteomics of R. varieornatus
        as one of two novel protein families (CAHS and SAHS) abundantly expressed in
        anhydrobiotic tardigrades.
    - statement: >-
        SAHS proteins are secretory, rich in beta-structure in hydrated conditions,
        and shift to alpha-helical conformation under water-deficient conditions.
    - statement: >-
        SAHS proteins are proposed to act as molecular shields during desiccation.
- id: PMID:27649274
  title: >-
    Extremotolerant tardigrade genome and improved radiotolerance of human cultured
    cells by tardigrade-unique protein
  findings:
    - statement: >-
        R. varieornatus genome encodes 13 SAHS genes; SAHS family members are
        constitutively and abundantly expressed.
    - statement: >-
        SAHS proteins maintain solubility after heat treatment and are proposed to
        protect biomolecules during desiccation.
- id: PMID:28703282
  title: >-
    Structural insights into a secretory abundant heat-soluble protein from an
    anhydrobiotic tardigrade, Ramazzottius varieornatus
  findings:
    - statement: >-
        Crystal structure of RvSAHS1 reveals a beta-barrel fold similar to FABPs with
        two putative ligand binding sites, establishing SAHS as a new FABP family.
    - statement: >-
        Hydrophilic residues form peculiar hydrogen bond networks in the SAHS1 structure,
        which may provide better tolerance against dehydration.
- id: PMID:29493034
  title: >-
    Crystal structure of secretory abundant heat soluble protein 4 from one of the
    toughest water bears micro-animals Ramazzottius Varieornatus
  findings:
    - statement: >-
        SAHS4 has different amino acid residues at ligand binding sites compared to SAHS1,
        preferring uncharged molecules, suggesting functional diversification within the
        SAHS family.

SAHS2

Gene Description

Existing Annotations Review

References

📚 Additional Documentation

Deep Research Falcon

Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

Target Gene/Protein Identity (from UniProt):

MANDATORY VERIFICATION STEPS:

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Output

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

Target Gene/Protein Identity (from UniProt):

MANDATORY VERIFICATION STEPS:

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Research report: Functional annotation of SAHS2 (UniProt J7MAN2) from Ramazzottius varieornatus

0) Target verification (gene/protein identity)

1) Key concepts and current understanding

1.1. What are SAHS proteins?

1.2. Stress biology concept: dehydration-driven structural plasticity

2) SAHS2: likely molecular function and mechanism (evidence-weighted)

2.1. Primary inferred function: extracellular/membrane-associated desiccation protection

2.2. Proposed mechanism: dehydration-driven conformational change and higher-order assemblies

3) Cellular and organismal context: expression and localization

3.1. Secretory nature (signal peptide; secretion)

3.2. Tissue/cell specificity in R. varieornatus (major 2023 advance)

4) Evolutionary and comparative context (expert analysis from authoritative sources)

4.1. Tardigrade-specific innovation

4.2. Gene family dynamics (2024 phylogenomic synthesis)

5) Applications and real-world implementations (2024 focus)

6) Quantitative highlights (recent studies prioritized)

7) Practical functional annotation summary for SAHS2 (UniProt J7MAN2)

Evidence summary table

Key figures supporting quantitative claims (Lim et al., 2024)

References (URLs and publication dates)

Citations

📄 View Raw YAML