Characterization of high-affinity protein D binding sites on the surface of rat epididymal spermatozoa.
125I-labeled protein D was shown to bind to whole rat epididymal sperm in a time-dependent, saturable, and reversible manner. Scatchard analysis indicates that there are 3.4 x 10(5) binding sites/sperm cell with a binding efficiency (Kd) of 2.3 x 10(-10) M. Binding of protein D to sperm reaches equilibrium by 95 min. and is reversible by 30 min. Specific binding of protein D to sperm pre-treated with a dilute trypsin solution is reduced significantly when compared with controls. Our findings establish that protein D-specific binding proteins displaying characteristics of a true receptor are present on the surface of rat epididymal sperm.
Hall
J C
JC
Department of Biochemistry, North Carolina State University, Raleigh 27695-7622, USA.
Tubbs
C E
CE
Li
Y
Y
Ashraf
S
S
D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D030501:Epididymal Secretory Proteins; D004822:Epididymis; D007700:Kinetics; D008297:Male; D008667:Metalloproteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013094:Spermatozoa / Q000378:metabolism*; D013735:Testicular Hormones / Q000378:metabolism*
D030501:Epididymal Secretory Proteins; D008667:Metalloproteins; D011956:Receptors, Cell Surface; D013735:Testicular Hormones