J Biol Chem, Vol. 274, Issue 2, 649-656, January 8, 1999

DNA-interacting Proteins in the Spermiogenesis of the Mollusc Murex brandaris

Carme Càceres, Pepita Giménez-Bonafé, Enric Ribes^¶, Danielle Wouters-Tyrou, Arlette Martinage, Mostafa Kouach, Pierre Sautière, Sylviane Muller^**, Jaume Palau, Juan A. Subirana, Luis Cornudella^§§, and Manel Chiva

From the  Departament d'Enginyeria Química, Escola Tècnica Superior d'Enginyers Industrials de Barcelona, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain, the ^¶ Departament Biología Cellular Animal Vegetal, Facultat Biología, Universitat de Barcelona, 08028 Barcelona, Spain,  URA, CNRS 1309, Chimie des Biomolécules, Institut Pasteur, 59019 Lille, France, ^** Institut Biologie Moléculaire Cellullaire, UPR 9021, CNRS, 67084 Strasbourg, France,  Departament d'Enginyeria Química Bioquímica, Facultat Ciències, Universitat Rovira i Virgili, 43005 Tarragona, Spain, and ^§§ Departament Molecular Cellular Biología, Institut Biología Molecular, Centro Investigacion y Desarrollo-Consejo Superior de Investigaciones Científicas, 08028 Barcelona, Spain

Sperm chromatin of Murex brandaris (a neogastropod mollusc) undergoes a series of structural transitions during spermiogenesis. The DNA-interacting proteins responsible for these changes as well as the mature protamines present in the ripe sperm nucleus have been characterized. The results reveal that spermiogenic nuclear proteins are protamine precursors that are subjected to a substantial number of small N-terminal deletions that gradually modify their overall charge. The composition of mature protamines is remarkably simple in turn, promoting an efficient and extremely tight packaging of DNA. The pattern of spermiogenic chromatin condensation in M. brandaris clearly departs from that corresponding to vertebrate chromatin.