Complete localization of the disulfide bridges and glycosylation sites in boar sperm acrosin

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Abstract
Acrosin is a disulfide-bonded two-chain glycoprotein, which belongs to the serine proteinase family and which plays a central role in mammalian fertilization. The amino acid sequence of acrosin from different species has been recently derived by cDNA analysis. Boar sperm acrosin contains twelve cysteine residues forming two interchain and 4 intrachain disulfide bonds. Protein-chemical and mass-spectroscopic analyses of fragments and subfragments obtained by proteolytic and chemical degradation of the isolated protein allowed the unambiguous localization of all disulfide bridges and glycosylation points in boar acrosin. The 12 cysteines and the glycosylated asparagines in the porcine enzyme are absolutely conserved in number and position within all known acrosin sequences. Thus, the disulfide bond and glycosylation patterns outlined here are conserved during evolution and may be important for enzyme function.