I D Donne | PubMed Health

PubMed1992

Xenopus laevis sperm proteins, previously identified as surface proteins with egg coat binding capability, are indeed histone H4, histone H3, and sperm specific protein SP2.

Recently, four Xenopus sperm proteins thought to be involved in binding to the egg envelope were identified (Lindsay and Hedrick, J. Exp. Zool., 245:286-293, '88). We have studied the three more abundant ones of apparent molecular weight of 14, 19, and 25 kd in SDS-PAGE. We have shown that these proteins are indeed nuclear basic proteins: the 14 kd is the histone H4, the 19 kd is the histone H3, and the 25 kd is the sperm-specific protein SP2.

Amino Acid Sequence↗

PubMed1991

Lithium increases actin polymerization rates by enhancing the nucleation step.

Lithium affects the polymerization mechanism of some cytoskeletal proteins in vitro, so its biological activity could also reflect lithium influence on assembly processes. Our data demonstrate that lithium nucleates actin polymerization and, in parallel, is less effective in the elongation step. Furthermore, falling-ball and fluorimetric tests suggested that lithium-induced actin polymers at steady-state are shorter than K(+)-polymerized actin filamentous structures. The lithium-induced actin assembly seems to follow the "reversible polymerization model" and the critical concentration of Li(+)-assembled actin at steady-state is markedly lower than that of sister actin samples polymerized by potassium chloride. Finally, the stabilization of actin nuclei induced by lithium ions could be related to their effect of lowering the dissociation rate constant.

Actin Cytoskeleton↗