The amino acid sequence of topi pancreatic ribonuclease

Pancreatic tissue from topi (Damaliscus korrigum) contains three ribonuclease components in a ratio of 8:22:70. Two components are glycosidated, whereas the third one does not contain carbohydrate. The amino acid sequence of topi ribonuclease A was deduced from a tryptic digest of the performic acid-oxidized protein. Peptides were positioned by homology with other bovid ribonucleases. Only peptides that differed in amino acid composition from the corresponding peptides of bovine ribonuclease were sequenced. The evidence obtained for the sequence of residues 67-73 is incomplete. Among the bovid ribonucleases (cow, bison, eland, sheep, goat and gnu), topi ribonuclease shows the closest resemblance with sheep and goat ribonucleases; except that the glutamic acid residue at position 103 in the ribonucleases from sheep and goat is substituted by a lysine residue in topi. Topi ribonucleases A and B differ only in the presence of carbohydrate attached to asparagine 34.