Identification of seminal proteins related to fertility of bulls

Abstract

These studies were conducted to determine the chemical identity of heparin binding proteins in semen that are related to fertility of bulls. The first study describes the isolation and identification of a 31,000 dalton fertility-associated antigen (FAA). FAA was found to have significant primary structure homology to a recently described novel DNase I-like protein. The physiological significance of the similarities between FAA and a protein homologous to DNase I is unknown at this time as no function has been described for the DNase I-like protein. The second study describes the isolation and identification of a 24,000 dalton seminal heparin binding protein. It was found to be similar, if not identical, to tissue inhibitor of metalloproteinase-2 (TIMP-2). TIMP-2 regulates matrix metalloprotease activity and therefore, potentially plays a key role in the structural makeup of the extracellular matrix. These findings suggest that regulation of enzymatic activity in seminal fluid is in large part a function of heparin binding proteins that have been correlated to fertility of bulls, one being a potentially novel extracellular nuclease and a second acting as a specific inhibitor of metalloprotease activity. In addition to the ability to modulate capacitation of sperm, seminal heparin binding proteins likely are key players in protecting sperm and male reproductive tract tissues from enzymatic hydrolysis. The proteins identified in this dissertation represent novel additions to the previously described seminal heparin binding protein families. Clearly, these data indicate a growing complexity of seminal fluid and implicate a novel Dnase I-like protein and TIMP-2 in affecting cellular events related to fertility potential of males.