IDENTIFICATION OF THE RAT EPIDIDYMIS-SECRETED 4E9 ANTIGEN AS PROTEIN-E - FURTHER BIOCHEMICAL-CHARACTERIZATION OF THE HIGHLY HOMOLOGOUS EPIDIDYMAL SECRETORY PROTEIN-D AND PROTEIN-E

Epididymis-secreted proteins D and E have been purified to homogeneity and partially characterized, and it is shown that monoclonal antibody (MAb) 4E9 (raised against a detergent extract of rat caudal epididyma l sperm [Moore et al., 1994: Mol Reprod Dev 37(2):181-194]) recognizes protein E, but not protein D. The molecular weight of protein D (simi lar to 30 kD) is similar to 2 kD lower than protein E (similar to 32 k D). The NH2-terminus of each protein is blocked; however, microsequenc ing of internal peptides confirms earlier reports of significant seque nce identity between the two proteins. High performance liquid chromat ography tryptic peptide mapping showed peak differences between the tw o proteins, but it was not possible to obtain amino acid sequence in t he peaks that were different. The epitope for MAb 4E9 was localized in the blocked NH2-terminus-CNBr peptide derived from protein E. The epi tope was destroyed by protease treatment of protein E. Removal of N-li nked oligosaccharides did not destroy the epitope for MAb 4E9 and did not affect the molecular weight difference between the proteins. (C) 1 996 Wiley-Liss, Inc.