Molecular characterization of caltrin-like proteins from human seminal plasma

ANAHÍ FRANCHI; CARLOS CORONEL

Villa General Belgrano, Córdoba, Argentina

Congreso; XIV Jornadas Científicas de la Sociedad de Biología de Córdoba; 2003

Sociedad de Biología de Córdoba

In the previous meeting we reported the presence of two protein fractions of 15 and 34 kDa in human seminal plasma that reacted with caltrin antibodies and were designated caltrin-like proteins. A procedure for purification and the first 35 aminoacid residues of the 15 kDa protein (p15) were also reported. This fragment showed homology with three proteins previously isolated from human prostate and seminal vesicles but their functions are still unknown. In this communication a comparative study on the molecular characteristics and structural differences between p15 and p34 are presented. The purification procedure for p15 was modified changing the step of saline fractionation and using Sephadex G-70 for exclusion chromatography to purify p34. The pIs estimated by isoelectrofocusing were 5.8 and 7.0 for p15 and p34 respectively. When both proteins were submitted to SDS-PAGE under no-reducing conditions, p15 showed a mixture of monomer and dimmer molecules in the native state while p34 moved as a 27 kDa protein suggesting the presence of disulfide bridges between Cys residues of the same polypeptide chain. The presence of sugars was assessed by periodic acid staining (PAS) or by specific interaction with ConA and WGA lectins conjugated with alkaline phosphatase (AP). Positive PSA and ConA assay obtained for p34 suggest the presence of carbohydrates likely bound by N-glycosidic bonds to the polypeptide chain. The structural differences between p15 and p34 may be associated to specific functions as it was determined with caltrin proteins from other species.