Recognition events and interactions between rat caltrin and model membranes.

GRASSO, ERNESTO J.; SOTTILE, EMILIANO; CORONEL, CARLOS E.

Santiago del Estero

Congreso; XLIV Reunion Anual de la Sociedad Argentina de Biofisica; 2015

Fresh mammalian spermatozoa are not able to fertilizeoocytes at the time of ejaculation; they become fertilization competent in thefemale reproductive tract where they undergo a series of biochemical andphysiological changes collectively designed as capacitation. It is known thatrat caltrin (calcium transport inhibitor) protein, bindsto the head of rat sperm cells during ejaculation, and inhibits theextracellular calcium uptake. Consequently, the spontaneous acrosome reactionis also inhibited leaving the sperm cells competent forfertilization. Although the sequence and biological effects of rat caltrin areknown, the interactions and mechanisms of binding to sperm membranes have notbeen explored. We first determined the rat caltrin tridimensional structure bymolecular homology modelling. Surface electrostatic potentials and electricfields were calculated using the Poisson-Boltzmann equation. Kyte and DoolittleHydropathy score was obtained using Expasy protscale tool. Equilibriumspreading pressure was obtained by Gibbs adsorption isotherms. Interactionsbetween caltrin and phospholipids model membranes were defined by penetration(cut off) studies. We observed that rat caltrin is able to penetrate directlyto membranes, but mainly in negatively charged surfaces and expanded lateralphase states.