Acrosome Biogenesis in the Hamster: DISCUSSION(4)
The protease(s) responsible for the intra-acrosomal size processing of the 40-kDa polypeptide in the hamster or of the SPlO-related proteins in other species are unidentified. In the hamster, the size processing results in two major polypeptides, AM22 and AM29, as well as a set of minor related bands; however, in other species such as the human, baboon, mouse, and bovine, the processing results in a family of several polypeptides but does not appear to result in the production of two major forms . The functional significance of these multiple polypeptide forms is unclear.
As suggested above, in the hamster they may assemble into distinct matrix regions, and it is also possible that they may have different hydrolase-binding properties. We have previously demonstrated by blot overlay analyses that AM29, but not AM22, exhibits proacrosin-binding activity , and whether AM22 binds other hydrolases has not been established. Possibly the multiple polypeptides in other species also have different hydrolase-binding specificity or affinity, but this has not been addressed. Our data show that the monoclonal anti-AM29/22 does not recognize the precursor 40-kDa polypeptide. This raises the possibility that in addition to size processing, the polypeptides may undergo further posttranslational modifications within the acrosome that are required for recognition by the monoclonal but not the polyclonal antibody. buy asthma inhaler