Binding of recombinant human proacrosin/acrosin to ZP glycoproteins. II. Participation of mannose residues in the interaction

FURLONG LI; VEAUTE C; VAZQUEZ-LEVIN MH

FERTILITY AND STERILITY

Elsevier

Lugar: Nueva York, NY; EEUU; Año: 2005 vol. 83 p. 1791 - 1796

0015-0282

Objective: To assess the interaction of human proacrosin/acrosin with mannose residues coupled to a protein backbone. Design: Prospective study. Setting: Basic research laboratory. Patient(s): Recombinant proteins derived from human proacrosin (Rec-40, Rec-30, Rec-20, Rec-10, and Rec-6) and bovine serum albumin (BSA)–mannose as ligand. Intervention(s): In vitro binding assay developed to assess proacrosin/acrosin–BSA–mannose interaction. Main Outcome Measure(s): Proacrosin/acrosin binding to BSA–mannose; estimation of binding affinity. Result(s): All recombinant proteins of acrosin but Rec-6 (residues 1–59 of proacrosin) specifically bound to BSA–mannose. Rec-40 (proacrosin) showed the highest binding affinity (dissociation constant Kd, 162 nM), followed by N-terminal fragments Rec-30 (248 nM), Rec-20 (359 nM), and Rec-10 (402 nM). A significant decrease in binding activity was observed when acrosin proteins were treated with denaturing agents such as urea or heat. The beta-mercaptoethanol treatment produced a 39% decrease on Rec-30 binding to BSA–mannose; in contrast, no effect was observed with Rec-40, suggesting the presence of at least two types of mannose-binding sites. Conclusion(s): [1] Proacrosin interacts with mannose residues through binding sites located at both the N- and C-terminal portion of the protein, [2] the full-length protein is required for maximal BSA–mannose binding, and [3] binding sites are stabilized by noncovalent bonds and by disulfide linkages.