The main objective of this work was to unequivocally determine the C- terminal sequence of human milk free secretory component (SC). It was found to end at arginine-585, i.e. 33 amino acids downstream from the major heterogeneous C-terminal residue previously identified for colostrum SC. In contrast, our data showed that the C-terminal end of SC was found to be homogeneous. Conflicting assignments, Asp/Gln, a missing Asn-211, Asp/Asn, Glu/Gln were corrected and found to agree with the cDNA sequence. An Ala/Val substitution at position 562 (domain VI) was identified. Its genetic significance is uncertain at present.
Hughes, G. J., Frutiger, S., Savoy, L. A., Reason, A. J., Morris, H. R., & Jaton, J. C. (1997). Human free secretory component is composed of the first 585 amino acid residues of the polymeric immunoglobulin receptor. FEBS Letters, 410(2–3), 443–446. https://doi.org/10.1016/S0014-5793(97)00629-7