CHARACTERIZATION OF CHROMATIN-CONDENSING PROTEINS DURING SPERMIOGENESIS IN A NEOGASTROPOD MOLLUSK (MUREX BRANDARIS)

During the process of chromatin condensation in the spermiogenesis of the neogastropod mollusc Murex brandaris, the nuclear protein compleme nt undergoes a complex series of changes. These changes lead to the ap pearance of three small protamines in the ripe sperm nuclei. We have c haracterized this system electrophoretically and at the compositional level, as well as through the analysis of crossreactions with antibodi es elicited against a specific spermatozoan protamine. Our results ind icate that the complex pattern of chromatin condensation during spermi ogenesis in this species (M. brandaris) may be modulated by a series o f post-translational (and intranuclear) modifications of DNA-interacti ng proteins, such as precursors to the sperm protamines. The amino aci d composition of each sperm protamine is remarkably simple (lys + arg + gly greater than or equal to 96 mol%). This system of spermiogenic/s permatozoal proteins in the neogastropod M. brandaris clearly differs from that in patellogastropods and archaeogastropods, and it may be he lpful in understanding evolutionary changes in the chromatin condensat ion pattern during the spermiogenesis of gastropod molluscs. (C) 1994 Wiley-Liss, Inc.