Purification and characterization of fertility-associated antigen (FAA) inbovine seminal fluid

Heparin-binding proteins (HBP) recognized by a monoclonal antibody (M1) ave produced by male accessory sex glands and bind to distinct regions of ejac ulated bull sperm. Immunoblots of sperm proteins probed with M1 identified HBP variants of approximately 31-, 24-, and 21.5-kDa that were associated w ith increased fertility of bulls. The purpose of this study was to identify the 31-kDa HBP known as fertility-associated antigen (FAA). FAA was isolat ed by heparin-affinity chromatography and reversed-phase high performance l iquid chromatography near homogeneity. Biochemical characterization indicat ed that FAA was an unglycosylated, basic protein. FAA protein was detected in seminal vesicle and prostate gland homogenates, and FAA extracted from s perm membranes by treatment with hypertonic media was identical biochemical ly to seminal fluid-derived FAA. N-terminal sequence analysis of purified F AA yielded a 26 amino acid sequence (L K I X S F N V R S F G E S K K A G F N A M R V I V) with 73% identity to a recently identified human deoxyribonu clease (DNase) I-like protein. Two internal amino acid sequences generated from lys-C digested FAA were 85% and 92% identical to the same DNase I-like protein. In conclusion, we have identified a bovine seminal heparin-bindin g protein that binds to sperm and is indicative of bull fertility as being similar to the family of DNase I-like proteins. These data demonstrate the presence of a novel DNase l-like protein in bull accessory sex glands and f orm the groundwork for the identification of a candidate genetic marker for fertility of bulls. (C) 1999 Wiley-Liss, Inc.