K9IWX5 is a secreted cysteine-rich protein of the CAP/SCP/TAPS superfamily (antigen 5 / CRISP subfamily) encoded in the submaxillary salivary gland transcriptome of the common vampire bat. The 241-residue precursor carries a predicted N-terminal signal peptide (residues 1-22), a CAP/PR-1 domain, and a C-terminal cysteine-rich ShKT module (residues 206-239) stabilised by two disulfide bonds, giving the canonical two-domain CRISP architecture. Antigen 5/CRISP proteins were recovered both as transcripts and as peptides in the principal submaxillary gland proteome of D. rotundus, so the family is translated and not merely transcribed in the gland; delivery of this specific protein into expectorated saliva has not been directly demonstrated. Its molecular activity is not established: CAP-superfamily members in vertebrate reproductive tracts, snake venoms, and the salivary glands of blood-feeding arthropods have been variously reported to bind lipids or divalent cations through the CAP cavity and to modulate ion channels through the cysteine-rich domain, but no activity has been demonstrated for any vampire bat CRISP, and the family is explicitly described as functionally uncharacterised in hematophagous salivary glands. The ShKT module of this protein is itself degenerate at residues that are conserved in canonical ShKT domains.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005576
extracellular region
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: Secretion is well supported for this protein and is independent of the UniProt CAUTION. The precursor has a SignalP-predicted signal peptide (residues 1-22) with a cleaved 23-241 chain, the CRISP family is a family of secreted proteins, and antigen-5/CRISP peptides were recovered from the principal submaxillary gland proteome of D. rotundus by LC-MS/MS. The CAUTION in the UniProt record refers to PROSITE ProRule PRU01005, i.e. the ShKT domain feature annotation, not to subcellular localisation.
Reason: Signal peptide prediction, CRISP family membership, and direct proteomic detection of antigen-5/CRISP family members in vampire bat salivary gland secretions all support extracellular localisation. The generic parent term GO:0005576 is retained rather than the child GO:0005615 (extracellular space) because there is no evidence distinguishing the soluble salivary pool from matrix-associated forms.
Supporting Evidence:
file:DESRO/K9IWX5/K9IWX5-uniprot.txt
SIGNAL 1..22
file:DESRO/K9IWX5/K9IWX5-uniprot.txt
Belongs to the CRISP family.
PMID:23411029
secretoglobin (65 ions) and antigen-5/CRISP families (57)
|
Q: Is the abundant salivary antigen-5/CRISP of Desmodus rotundus active on host hemostasis, vascular tone, or nociception at the bite site, or is it a functionally inert secretory product?
Suggested experts: Ivo M. B. Francischetti, José M. C. Ribeiro
Q: Do vampire bat salivary CRISPs show the signature of positive selection seen in vampire bat lysozyme, which would indicate adaptation to sanguivory rather than neutral retention?
Q: Does the degenerate ShKT module of K9IWX5 retain any ion-channel activity, and if not, has the CAP domain taken over as the functional module?
Experiment: Express the mature 23-241 chain in a eukaryotic system that supports extensive disulfide bonding (UniProt annotates only the two ShKT bonds 215-233 and 224-237, but the mature chain carries 16 cysteines, so up to eight bonds are expected for the CRISP fold; e.g. Drosophila S2 or Expi293), confirm fold by circular dichroism, then screen against a panel of host K+ (BKCa, Kv1.1, Kv1.3) and Ca2+ channels by whole-cell patch clamp, and on cytokine release from human monocytes.
Hypothesis: Recombinant mature K9IWX5 modulates host ion channels or inflammatory signalling at the feeding site, analogous to characterised venom CRISPs.
Type: Recombinant expression plus electrophysiology and cytokine assay
Experiment: Perform lipidomic pull-down on recombinant K9IWX5 from host plasma and skin homogenate, and test binding of candidate prohemostatic prostaglandins (PGE2, PGF2-alpha, thromboxane) by isothermal titration calorimetry, using a CAP-cavity histidine mutant as the negative control.
Hypothesis: The CAP cavity of K9IWX5 binds a small hydrophobic ligand (sterol, fatty acid, or eicosanoid) that it scavenges or delivers at the bite site.
Type: Ligand pull-down and isothermal titration calorimetry
Experiment: Raise antibodies against recombinant K9IWX5 and assay saliva collected directly from feeding vampire bats by Western blot and targeted parallel reaction monitoring mass spectrometry, comparing principal and accessory gland extracts with expectorated saliva.
Hypothesis: K9IWX5 is secreted into saliva rather than retained in the gland, and is transferred to the host during feeding.
Type: Targeted proteomics of expectorated saliva
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.
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
| Item | K9IWX5 annotation / evidence | Key sources (year, URL) |
|---|---|---|
| Identity | UniProt accession K9IWX5 — annotated as a putative SCP/Tpx1/CRISP-like extracellular protein from Desmodus rotundus (vampire bat); no curated gene symbol in UniProt. | UniProt/InterPro annotation summary (IPR entries) and CAP/CRISP family notes (Hubbard 2024) (hubbard2024theidentificationand pages 89-92). |
| Domain architecture | Predicted N-terminal CAP/PR-1 (SCP/TAPS) domain, hinge region, and C-terminal cysteine-rich domain (CRD) typical of CRISP proteins; overall CRISP family fold and conserved cysteines inferred. | CRISP/CAP domain architecture descriptions (AlShammari 2023, Rao 2024); InterPro domain annotations (Hubbard 2024) — AlShammari 2023: https://doi.org/10.3390/toxins16010012 (alshammari2023snakevenoma pages 18-19); Rao 2024: https://doi.org/10.3390/toxins16120519 (rao2024theroleof pages 25-26); Hubbard 2024 (hubbard2024theidentificationand pages 67-70). |
| InterPro signatures | Reported InterPro entries: IPR014044 (CAP_dom), IPR035940 (CAP_sf), IPR042076 (Crisp-like_dom), IPR001283 (CRISP-related), IPR018244 (Allrgn_V5/Tpx1_CS) — annotated in UniProt metadata for K9IWX5. | InterPro/UniProt annotations and CAP family surveys (Hubbard 2024) (hubbard2024theidentificationand pages 67-70). |
| Predicted localization | Signal peptide / secreted extracellular localization predicted (consistent with CRISP family secretory proteins and UniProt annotation). | Secreted CRISP family description and gland/secretome occurrence (Rodrigo 2021; Hubbard 2024) — Rodrigo 2021: https://doi.org/10.3390/toxins13020097 (rodrigo2021atranscriptomicapproacha pages 4-6); Hubbard 2024 (hubbard2024theidentificationand pages 67-70). |
| Evidence type | Database annotation (UniProt / InterPro); no primary experimental characterization found for this specific accession (K9IWX5) — functional inferences rely on family/domain homology. | UniProt/InterPro metadata cross-referenced with literature-level family function (Hubbard 2024, Rodrigo 2021) (hubbard2024theidentificationand pages 67-70, rodrigo2021atranscriptomicapproacha pages 4-6). |
| Literature anchors for functional inference | Mammalian CRISPs (CRISP1–4) — roles in reproduction, sperm/epididymal function, and ion-channel regulation; Venom CRISPs — ion-channel blockade (Ca2+, K+), proinflammatory actions; these family activities provide the most plausible functional hypotheses for K9IWX5 (if secreted in saliva/glands). | Mammalian reproductive/epididymal CRISP role (Sulzyk et al. 2024 bioRxiv: https://doi.org/10.1101/2024.03.19.585807) (sulzyk2024contributionofthe pages 1-4); Venom CRISP ion-channel/inflammatory activities (AlShammari 2023: https://doi.org/10.3390/toxins16010012; Rao 2024: https://doi.org/10.3390/toxins16120519) (alshammari2023snakevenoma pages 18-19, rao2024theroleof pages 25-26); CAP family context/InterPro usage (Hubbard 2024) (hubbard2024theidentificationand pages 67-70). |
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)
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
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
5) Relevant statistics and data from recent studies
Functional annotation for K9IWX5 (evidence-based inference)
Limitations and data gaps
References (with URLs and dates)
References
(hubbard2024theidentificationand pages 67-70): IC Hubbard. The identification and testing of novel vaccine candidates against whipworm. Unknown journal, 2024.
(hubbard2024theidentificationand pages 89-92): IC Hubbard. The identification and testing of novel vaccine candidates against whipworm. Unknown journal, 2024.
(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.
(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.
(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.
(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.
(goncalves2025coleoidvenomspredicting pages 68-70): CVC Gonçalves. Coleoid venoms: predicting cephalotoxin function and biotechnological applications from ecological and evolutionary traits. Unknown journal, 2025.
Traced the provenance of this entry. The EMBL record behind K9IWX5 (JAA45881.1,
TISSUE=Salivary gland) comes from the "Vampirome" study of the D. rotundus
submaxillary glands, now cached as PMID:23411029. That paper is directly usable
as a reference for this protein and resolves two things the review previously
had to leave open:
PROSITE-ProRule:PRU01005, which is the ShKT rule —GO:0005576 from UNDECIDED to ACCEPTmolecular_function term, plusDeliberately did not import the deep-research file's CRISP ion-channel and
reproduction narrative as positive evidence: it is family-level inference drawn
largely from snake-venom reviews that the report itself flags as low-quality
journals, and none of it concerns Desmodus. Marked that reference
relevance: MEDIUM / correctness: UNVERIFIED.
Addressed the PR review on the weekly-compliance-2026-07-31-K9IWX5 branch:
description and the PMID:23411029findings statement asserted that the protein is "a bona fide component ofsuggested_experiments #3, that proposes to test exactly this.GO:0005576 ACCEPT is unaffected: signal peptide + cleaved chain + CRISPdescription. Perdescription is a project-independent biologicalknowledge_gaps entry.InterPro; IPR018244; Allrgn_V5/Tpx1_CS.DR line from the UniProt record, not text of GO_REF:0000002, so it nowfile:DESRO/K9IWX5/K9IWX5-uniprot.txt reference. The GO_REFsupporting_text, matching the conventionGO:0005576 supported_by.correctness: UNVERIFIED with review_notes saying itsuggested_experiments #1: UniProtid: K9IWX5
gene_symbol: K9IWX5
product_type: PROTEIN
status: DRAFT
taxon:
id: NCBITaxon:9430
label: Desmodus rotundus
description: >-
K9IWX5 is a secreted cysteine-rich protein of the CAP/SCP/TAPS superfamily
(antigen 5 / CRISP subfamily) encoded in the submaxillary salivary gland
transcriptome of the common vampire bat. The 241-residue precursor carries a
predicted N-terminal signal peptide (residues 1-22), a CAP/PR-1 domain, and a
C-terminal cysteine-rich ShKT module (residues 206-239) stabilised by two
disulfide bonds, giving the canonical two-domain CRISP architecture. Antigen
5/CRISP proteins were recovered both as transcripts and as peptides in the
principal submaxillary gland proteome of D. rotundus, so the family is
translated and not merely transcribed in the gland; delivery of this specific
protein into expectorated saliva has not been directly demonstrated. Its
molecular activity is not established: CAP-superfamily members in vertebrate
reproductive tracts, snake venoms, and the salivary glands of blood-feeding
arthropods have been variously reported to bind lipids or divalent cations
through the CAP cavity and to modulate ion channels through the cysteine-rich
domain, but no activity has been demonstrated for any vampire bat CRISP, and
the family is explicitly described as functionally uncharacterised in
hematophagous salivary glands. The ShKT module of this protein is itself
degenerate at residues that are conserved in canonical ShKT domains.
existing_annotations:
- term:
id: GO:0005576
label: extracellular region
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: >-
Secretion is well supported for this protein and is independent of the
UniProt CAUTION. The precursor has a SignalP-predicted signal peptide
(residues 1-22) with a cleaved 23-241 chain, the CRISP family is a
family of secreted proteins, and antigen-5/CRISP peptides were recovered
from the principal submaxillary gland proteome of D. rotundus by
LC-MS/MS. The CAUTION in the UniProt record refers to PROSITE ProRule
PRU01005, i.e. the ShKT domain feature annotation, not to subcellular
localisation.
action: ACCEPT
reason: >-
Signal peptide prediction, CRISP family membership, and direct proteomic
detection of antigen-5/CRISP family members in vampire bat salivary
gland secretions all support extracellular localisation. The generic
parent term GO:0005576 is retained rather than the child GO:0005615
(extracellular space) because there is no evidence distinguishing the
soluble salivary pool from matrix-associated forms.
supported_by:
- reference_id: file:DESRO/K9IWX5/K9IWX5-uniprot.txt
supporting_text: 'SIGNAL 1..22'
- reference_id: file:DESRO/K9IWX5/K9IWX5-uniprot.txt
supporting_text: 'Belongs to the CRISP family.'
- reference_id: PMID:23411029
supporting_text: >-
secretoglobin (65 ions) and antigen-5/CRISP families (57)
reference_section_type: RESULTS
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with
GO terms
findings:
- statement: >-
InterPro signature IPR018244 (Allergen V5/Tpx1 conserved site) was used
to infer extracellular localisation for K9IWX5. This is a family-level
inference from the CAP/CRISP domain signature rather than direct
evidence for this protein. The InterPro cross-reference itself is
recorded on the UniProt record.
- id: PMID:23411029
title: 'The "Vampirome": Transcriptome and proteome analysis of the principal
and accessory submaxillary glands of the vampire bat Desmodus rotundus, a
vector of human rabies.'
findings:
- statement: >-
Antigen 5/CRISP family members are among the protein families sequenced
from the D. rotundus submaxillary salivary glands, and antigen-5/CRISP
peptides were recovered from the principal gland proteome by LC-MS/MS
(57 ions), showing that the family is translated in the gland rather
than only transcribed. The identification is family-level and was made
on dissected gland homogenate, so it does not by itself assign peptides
to K9IWX5 or demonstrate delivery into expectorated saliva.
supporting_text: >-
secretoglobin (65 ions) and antigen-5/CRISP families (57)
reference_section_type: RESULTS
- statement: >-
The authors state that the function of salivary antigen-5/CAP family
proteins is unknown apart from a few exceptions, and that function in
bat saliva can only be assigned after recombinant expression. This is
the field's own admission of ignorance for this protein family.
supporting_text: >-
With few exceptions [59, 116], their function is unknown.
reference_section_type: DISCUSSION
- statement: >-
Antigen-5 proteins belong to the larger CAP superfamily and are among
the most ubiquitous proteins in the salivary glands of blood-feeding
arthropods, indicating repeated recruitment of this fold into
hematophagous salivary secretomes.
supporting_text: >-
are among the most ubiquitous proteins in the SG of blood sucking arthropods
reference_section_type: DISCUSSION
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: >-
PubMed-verified. This is the source publication for the EMBL entry
(JAA45881.1) from which K9IWX5 was derived; the salivary gland tissue
attribution in the UniProt record traces to this transcriptome/proteome
study. It supports secretion and salivary-gland origin, and explicitly
states that the function of the salivary antigen-5/CRISP family is
unknown.
- id: file:DESRO/K9IWX5/K9IWX5-uniprot.txt
title: UniProtKB record for K9IWX5 (K9IWX5_DESRO)
findings:
- statement: >-
The precursor carries a SignalP-predicted signal peptide (1-22) and a
cleaved mature chain (23-241), and belongs to the CRISP family.
supporting_text: 'Belongs to the CRISP family.'
- statement: >-
The record carries the InterPro signature IPR018244 (Allergen
V5/Tpx1 conserved site) that GO_REF:0000002 used to infer
extracellular localisation.
supporting_text: 'InterPro; IPR018244; Allrgn_V5/Tpx1_CS.'
- statement: >-
A C-terminal ShKT domain (206-239) with two predicted disulfide bonds
(215-233, 224-237) completes the canonical CAP + cysteine-rich CRISP
architecture.
supporting_text: '/note="ShKT"'
- statement: >-
UniProt cautions that the sequence lacks conserved residues required
for propagating feature annotation under PROSITE ProRule PRU01005,
which is the ShKT rule. The caution therefore limits confidence in
ShKT-derived functional transfer, not in the secretion prediction.
supporting_text: >-
CAUTION: Lacks conserved residue(s) required for the propagation of
feature annotation.
- id: file:DESRO/K9IWX5/K9IWX5-deep-research-falcon.md
title: Deep research report on K9IWX5
findings:
- statement: >-
No protein-specific peer-reviewed studies exist for K9IWX5; all
functional statements beyond domain presence and predicted secretion
are family-level inferences.
supporting_text: >-
No peer-reviewed, protein-specific studies for K9IWX5 were found.
reference_review:
relevance: MEDIUM
correctness: UNVERIFIED
review_notes: >-
LLM-generated literature survey. Useful for the CAP/CRISP family
background and for its explicit statement that no protein-specific
studies exist, but several of its cited sources are flagged in the
report itself as low-quality journals, and none concerns Desmodus
rotundus. Not used here to support any positive functional claim.
core_functions:
- description: >-
Secreted CAP/CRISP-superfamily protein of the vampire bat submaxillary
salivary gland. A cleaved signal peptide and CRISP family membership place
the mature chain in the extracellular region, but no molecular activity
has been demonstrated for it or for any vampire bat CRISP, so no molecular
function term is asserted.
supported_by:
- reference_id: file:DESRO/K9IWX5/K9IWX5-uniprot.txt
supporting_text: 'Belongs to the CRISP family.'
- reference_id: PMID:23411029
supporting_text: >-
secretoglobin (65 ions) and antigen-5/CRISP families (57)
reference_section_type: RESULTS
locations:
- id: GO:0005576
label: extracellular region
knowledge_gaps:
- gap_statement: >-
The molecular activity of the vampire bat salivary antigen-5/CRISP
protein is undetermined: neither a ligand for the CAP cavity nor an
ion-channel or receptor target for the cysteine-rich C-terminal module
has been identified for K9IWX5 or any Desmodus CRISP.
boundary: >-
What is firmly established is the architecture and the secretion: a
cleaved signal peptide, a CAP/PR-1 domain, a C-terminal ShKT module
with two disulfide bonds, CRISP family membership, and recovery of
antigen-5/CRISP peptides from the principal submaxillary gland
proteome by LC-MS/MS.
gap_kind:
- BIOLOGY
dark_aspect: MF_DARK
status: OPEN
significance: >-
Vampire bat saliva is a source of characterised anti-hemostatic and
anti-inflammatory proteins; whether this abundant CRISP contributes to
host modulation at the bite site, or is a vestigial secretory product,
determines whether it belongs in the salivary pharmacopoeia at all.
resolution: >-
Recombinant expression of the mature 23-241 chain followed by
ion-channel electrophysiology, lipid/sterol binding assays for the CAP
cavity, and testing on host hemostatic and inflammatory readouts.
provenance:
- reference_id: PMID:23411029
supporting_text: >-
With few exceptions [59, 116], their function is unknown.
reference_section_type: DISCUSSION
- reference_id: PMID:23411029
supporting_text: >-
Evidently, the function of these proteins in bat saliva can only be
assigned after recombinant expression.
reference_section_type: DISCUSSION
- gap_statement: >-
It is undetermined whether the C-terminal ShKT module of K9IWX5 is
functional, because the sequence lacks conserved residues required for
propagating ShKT feature annotation.
boundary: >-
The module is detected by PROSITE PS51670 and two disulfides are
predicted, so the fold is present; what is unknown is whether the
degenerate residues abolish the potassium-channel-blocking activity
associated with canonical ShKT domains.
gap_kind:
- BIOLOGY
dark_aspect: MF_DARK
status: OPEN
significance: >-
ShKT modules are the structural basis for the ion-channel activity
attributed to venom CRISPs; a degenerate module would argue that this
salivary protein acts through its CAP domain instead.
resolution: >-
Site-resolved comparison against characterised ShKT domains plus
patch-clamp assays of the recombinant C-terminal module on Kv1.x
channels.
provenance:
- reference_id: file:DESRO/K9IWX5/K9IWX5-uniprot.txt
supporting_text: >-
CAUTION: Lacks conserved residue(s) required for the propagation of
feature annotation.
suggested_questions:
- question: >-
Is the abundant salivary antigen-5/CRISP of Desmodus rotundus active on
host hemostasis, vascular tone, or nociception at the bite site, or is it
a functionally inert secretory product?
experts:
- Ivo M. B. Francischetti
- José M. C. Ribeiro
- question: >-
Do vampire bat salivary CRISPs show the signature of positive selection
seen in vampire bat lysozyme, which would indicate adaptation to
sanguivory rather than neutral retention?
- question: >-
Does the degenerate ShKT module of K9IWX5 retain any ion-channel activity,
and if not, has the CAP domain taken over as the functional module?
suggested_experiments:
- hypothesis: >-
Recombinant mature K9IWX5 modulates host ion channels or inflammatory
signalling at the feeding site, analogous to characterised venom CRISPs.
description: >-
Express the mature 23-241 chain in a eukaryotic system that supports
extensive disulfide bonding (UniProt annotates only the two ShKT bonds
215-233 and 224-237, but the mature chain carries 16 cysteines, so up to
eight bonds are expected for the CRISP fold; e.g. Drosophila S2 or
Expi293), confirm fold by
circular dichroism, then screen against a panel of host K+ (BKCa, Kv1.1,
Kv1.3) and Ca2+ channels by whole-cell patch clamp, and on cytokine release
from human monocytes.
experiment_type: Recombinant expression plus electrophysiology and cytokine assay
- hypothesis: >-
The CAP cavity of K9IWX5 binds a small hydrophobic ligand (sterol, fatty
acid, or eicosanoid) that it scavenges or delivers at the bite site.
description: >-
Perform lipidomic pull-down on recombinant K9IWX5 from host plasma and skin
homogenate, and test binding of candidate prohemostatic prostaglandins
(PGE2, PGF2-alpha, thromboxane) by isothermal titration calorimetry, using
a CAP-cavity histidine mutant as the negative control.
experiment_type: Ligand pull-down and isothermal titration calorimetry
- hypothesis: >-
K9IWX5 is secreted into saliva rather than retained in the gland, and is
transferred to the host during feeding.
description: >-
Raise antibodies against recombinant K9IWX5 and assay saliva collected
directly from feeding vampire bats by Western blot and targeted parallel
reaction monitoring mass spectrometry, comparing principal and accessory
gland extracts with expectorated saliva.
experiment_type: Targeted proteomics of expectorated saliva