High and low molecular weight rabbit secretory components. Evidence for the deletion of the second and third domains in the smaller polypeptide.
Rabbit secretory components exist in two forms which differ in apparent mass by about 25 kDa. Each of these two forms were reduced, carboxymethylated, and extensively digested with trypsin. The resulting peptides were purified by reverse-phase high performance liquid chromatography and characterized by NH2- and COOH-terminal sequence determination and/or amino acid analysis. They were aligned with the protein sequence predicted from the cDNA nucleotide sequence encoding the rabbit poly(Ig) receptor (Mostov, K. E., Friedlander, M., and Blobel, G. (1984) Nature 308, 37-43). All peptides belonging to the fourth and fifth domains except one (positions 488-496) were accounted for in both forms. In addition, limited tryptic proteolysis of the native low Mr secretory components produced the intact 18-kDa NH2-terminal domain (positions 1-117) and the 30-kDa fragment encompassing the fourth and fifth domains. These results suggest that the smaller polypeptide derives from the larger secretory component form by the deletion of the second and third domains.
D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D007128:Immunoglobulin Fragments / Q000032:analysis*; D046911:Macromolecular Substances; D008970:Molecular Weight; D011817:Rabbits; D012635:Secretory Component / Q000032:analysis*; D014357:Trypsin / Q000378:metabolism
D007128:Immunoglobulin Fragments; D046911:Macromolecular Substances; D012635:Secretory Component; D014357:Trypsin