STAP-PSI domain is the key in the STAPS spermicidal activity

ROBUSCHI, L; MUÑOZ, F; DALEO, GR; CESARI, A; GUEVARA, MG

Villa Carlos Paz, Cordoba

Congreso; XLIV Reunion Anual de la SAIB; 2008

Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular

We have isolated two potato aspartic proteases (StAPs) with cytotoxic effect towards plant and human pathogens and on bovine and human sperm. StAPs exert its cytotoxic activity by selective plasma membrane permeabilization. Cytotoxic activity of StAPs is related with the presence in these proteins of a domain named Plant Specific Insert (PSI), which has high structural homology with proteins able to interact with different phospholipids (SAPLIPs). The aim of this work was to analyse the capacity of this domain, StAsp-PSIr, to interact with the plasma membrane and to exert spermicidal activity over bovine and human sperm, both cryopreserved and fresh. StAsp-PSIr reduced, in a dose-dependent manner (0.6-12,5 μM), bovine and human sperm total motility (100% at concentrations of 12,5 and 2,4μM respectively) and increased sperm membrane permeability (100 % at concentrations of 12,5 and 7,5μM respectively). These results suggest that StAsp- PSIr is the key domain into the StAPs to exert spermicidal activity. However, contrary with the results reported for StAPs, StAsp-PSIr was unable to bind to spermatozoa surface, independently of the specie and conservation method. Therefore, correct folding in the structure of mature protein or another StAPs domain is necessary for binding to spermatozoa surface.