Putative StAPs CD4-like receptor binding domain is involved in StAPs/spermatozoa surface interaction.

MUÑOZ FF, ROBUSCHI L, DALEO GR, AND GUEVARA MG

Mar del Plata

Congreso; Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2007

Potato aspartic proteases (StAPs) are plant proteases with antimicrobial activity. Previous results have shown that StAPs are spermicidal compounds. These proteins are able to interact with capacitated spermatozoa surface in the post-acrosomal region. Likewise, another aspartic protease from human seminal plasma, named gp17, interacts with spermatozoa in the same region that StAPs. This binding could be associated with gp17 capacity to interact with CD4-like receptor. Additionally, gp17 interferes with gp120 (HIV-type I envelope glycoprotein)/CD4 binding, although it binds to a different site but close to the gp120-binding site. The aim of this work was to analyse if the capacity of binding of StAPs to spermatozoa surface is associated to StAPs/CD4-like receptor binding. Besides, the presence of a putative StAPs-binding domain to CD4-like receptor was estimated by bioinformatic analysis. Results obtained from immunological analyses using monoclonal CD4 IgG antibodies show that StAPs are able to bind to CD4-like receptor of capacitated spermatozoa surface. Bioinformatic analysis shows a putative CD4 binding domain in StAPs structure. According with these results, StAPs interact with CD4-like receptor in a different domain that those described for gp17 or for gp120. The results obtained here suggest that StAPs could be analysed as a possible new gp120/CD4 blocker.