Tc. Mccauley et al., LOCALIZATION OF A HEPARIN-BINDING PROTEIN TO DISTINCT REGIONS OF BOVINE SPERM, Journal of animal science, 74(2), 1996, pp. 429-438
Heparin-binding proteins (HBP) in bull seminal fluid bind to epididyma
l sperm membranes at ejaculation. Peptides recognized by a monoclonal
antibody (M1) correspond to proteins identified in complexes that have
the greatest affinity for heparin and are present on sperm from bulls
with higher fertility. Presence of specific HBP on sperm regulates th
e ability of sperm to bind heparin, and heparin binding to sperm corre
lates with the fertility potential of a bull. In these studies, the in
teraction of HBP with sperm from 10 bulls of proven fertility was anal
yzed by immunofluorescence of M1 to determine the localization of hepa
rin-binding proteins during capacitation, and the fluorescent binding
patterns were compared to bull nonreturn rates. Immunofluorescent loca
lization of M1 binding sites revealed the existence of specific membra
ne domains containing HBP in acrosomal and postacrosomal regions of ej
aculated but not in epididymal sperm. Monoclonal antibody recognition
of HBP localized on membranes of sperm revealed variable binding patte
rns of M1 to the acrosomal region in sperm from bulls of known fertili
ty. Regression analysis indicated a negative relationship between sper
m displaying exclusively acrosomal fluorescence and bull nonreturn rat
e. These data indicate that HBP bind to sperm in distinct patterns, on
e of which differed among bulls of varying fertility, and indicate no
apparent relocalization of these sites during cellular changes that oc
cur in preparation for fertilization.