Boar acrosin is a two‐chain molecule: Isolation and primary structure of the light chain; homology with the pro‐part of other serine proteinases

Abstract

Acrosin (EC 3.4.21.10), the major proteinase of mammalian spermatozoa, has been demonstrated to be a two‐chain glycoprotein with an Mr‐4200 light chain covalently attached to an Mr‐37000 heavy chain. Following mercaptolysis of the disulfide bonds, the two chains were separated by high‐performance liquid chromatography on a reversed‐phase column. Sequence analysis of the isolated light chain (23 amino acid residues) indicated a considerable sequence homology with the bovine chymotrypsinogen activation peptide (6 out of 15 positions with identical amino acids, i.e. 40% identity) and the pro‐part of other serine proteinases (17–22% identity), thus suggesting that the acrosin light chain corresponds to the pro‐part of the acrosin zymogen. In position 3, the light chain confers a carbohydrate side chain N‐glycosidically linked to the acceptor sequence Asn‐Xaa‐Thr. Evidence is presented that the acrosin light chain is connected via two disulfide bridges to the heavy chain which contains about 320 amino acids including the active‐site residues of the proteinase. Copyright © 1984, Wiley Blackwell. All rights reserved