Sperm adhesion molecules: Structure and function

Fertilisation is a unique event in which the morphologically disparate game tes recognise, bind and fuse with each other. This event follows a highly r egulated schedule of biochemical interactions, in which molecules are invol ved that mediate cell adhesion, signal transduction and the initiation of m etabolic pathways. A plethora of molecules has been found on the male gamet e and with regard to the different protein structures it is almost impossib le to overlook the structures involved. Even more, carbohydrate structures cause an additional diversity with regard to the generation of surface stru ctures. In this communication we try to elucidate the structures of protein s that have been known so far. We have focussed on spermadhesins, the zonad hesin, proacrosin and the PH-20 antigen. The variety of structures and also the common features a mong them as well as the presence of redundant syste ms are attributable to the evolutionary force of intraspecific sperm compet ition. This evolutionary force is assumed to be also responsible for the sp ecies selectivity observed in these adhesion molecules, which explains the preferential binding of gametes in a homologous system. Copyright (C) 2001 S. Karger AG, Basel.