The 26 kD protein recognized on rat cauda epididymal sperm by monoclonal antibody 4E9 has internal peptide sequence that is identical to the secreted form of epididymal protein E.
MAb 4E9, raised against a detergent extract of rat cauda epididymal sperm, recognizes a 26 kD glycoprotein that is found on the plasma membrane of the sperm tail in cauda, but not caput, sperm (Moore et al., 1994). It also recognizes an epididymis-secreted protein that has been shown to be protein E (Xu and Hamilton, 1996). It is felt that the secreted protein becomes associated with sperm, but there has been no biochemical evidence of molecular identity between the secreted and membrane proteins. In this report, the membrane form of the antigen has been purified by reverse phase HPLC. Cyanogen bromide cleavage of the purified protein yielded 3 peptides that were purified, also by reverse phase HPLC. One of the peptides yielded an unambiguous sequence of 34 amino acids that is identical to an internal peptide of the protein found in epididymal fluid. This is the first report showing sequence identity between an epididymis-secreted protein and a protein of the sperm plasma membrane.
Xu
W
W
Dana-Farber Cancer Institute, Department of Pathology, Harvard Medical School, Boston, Massachusetts, USA.
Ensrud
K M
KM
Hamilton
D W
DW
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D002462:Cell Membrane / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D030501:Epididymal Secretory Proteins; D004822:Epididymis / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry* / Q000302:isolation & purification; D008667:Metalloproteins / Q000737:chemistry* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000737:chemistry* / Q000302:isolation & purification; D010449:Peptide Mapping; D051381:Rats; D013094:Spermatozoa / Q000737:chemistry*; D013735:Testicular Hormones / Q000737:chemistry* / Q000302:isolation & purification
D000911:Antibodies, Monoclonal; D030501:Epididymal Secretory Proteins; D008565:Membrane Proteins; D008667:Metalloproteins; D009687:Nuclear Proteins; D013735:Testicular Hormones; C086245:protein E, cuttlefish