1fiz
From Proteopedia
THREE DIMENSIONAL STRUCTURE OF BETA-ACROSIN FROM BOAR SPERMATOZOA
Overview
BACKGROUND: Proacrosin is a serine protease found specifically within the acrosomal vesicle of all mammalian spermatozoa. During fertilization proacrosin autoactivates to form beta-acrosin, in which there is a "light" chain cross-linked to a "heavy" chain by two disulphide bonds. beta-acrosin is thought to be multifunctional with roles in acrosomal exocytosis, as a receptor for zona pellucida proteins, and as a protease to facilitate penetration of spermatozoa into the egg. RESULTS: The crystal structures of both ram and boar beta-acrosins have been solved in complex with p-aminobenzamidine to 2.1 A and 2.9 A resolution, respectively. Both enzymes comprise a heavy chain with structural homology to trypsin, and a light chain covalently associated in a similar manner to blood coagulation enzymes. In crystals of boar beta-acrosin, the carboxyl terminus of the heavy chain is inserted into the active site of the neighboring molecule. In both enzyme structures, there are distinctive positively charged surface "patches" close to the active site, which associate with carbohydrate from adjacent molecules and also bind sulfate ions. CONCLUSIONS: From the three-dimensional structure of beta-acrosin, two separate effector sites are evident. First, proteolytic activity, believed to be important at various stages during fertilization, arises from the trypsin-like active site. Activity of this site may be autoregulated through intermolecular associations. Second, positively charged regions on the surface adjacent to the active site may act as receptors for binding zona pellucida glycoproteins. The spatial proximity of these two effector sites suggests there may be synergy between them.
About this Structure
1FIZ is a Protein complex structure of sequences from Sus scrofa. Full crystallographic information is available from OCA.
Reference
Effector sites in the three-dimensional structure of mammalian sperm beta-acrosin., Tranter R, Read JA, Jones R, Brady RL, Structure. 2000 Nov 15;8(11):1179-88. PMID:11080640 Page seeded by OCA on Fri May 2 16:23:02 2008
