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.

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.

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.

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.

The precursor carries a SignalP-predicted signal peptide (1-22) and a cleaved mature chain (23-241), and belongs to the CRISP family.

The record carries the InterPro signature IPR018244 (Allergen V5/Tpx1 conserved site) that GO_REF:0000002 used to infer extracellular localisation.

A C-terminal ShKT domain (206-239) with two predicted disulfide bonds (215-233, 224-237) completes the canonical CAP + cysteine-rich CRISP architecture.

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.

No protein-specific peer-reviewed studies exist for K9IWX5; all functional statements beyond domain presence and predicted secretion are family-level inferences.