Proteolytic processing of a protein involved in sperm-egg fusion correlates with acquisition of fertilization competence.
A protein located on the surface of guinea pig sperm (PH-30) has been implicated in the process of sperm-egg fusion (Primakoff, P., H. Hyatt, and J. Tredick-Kline. 1987. J. Cell Biol. 104:141-149). In this paper we have assessed basic biochemical properties of PH-30 and have analyzed the molecular forms of PH-30 present at different stages of sperm maturation. We show the following: (a) PH-30 is an integral membrane glycoprotein; (b) it is composed of two tightly associated and immunologically distinct subunits; (c) both subunits are made as larger precursors; (d) processing of the two subunits occurs at different developmental stages; (e) the final processing step occurs in the region of the epididymis where sperm become fertilization competent; (f) processing can be mimicked in vitro; (g) processing exposes at least two new epitopes on PH-30-one of the newly exposed epitopes is recognized by a fusion-inhibitory monoclonal antibody. These results are discussed in terms of the possible role of PH-30 in mediating fusion with the egg plasma membrane.
Blobel
C P
CP
Department of Biochemistry, University of California, San Francisco 94143-0450.
Myles
D G
DG
Primakoff
P
P
White
J M
JM
D000818:Animals; D000911:Antibodies, Monoclonal; D002846:Chromatography, Affinity; D005260:Female; D005306:Fertilization; D006026:Glycoside Hydrolases; D006168:Guinea Pigs; D046911:Macromolecular Substances; D008297:Male; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology*; D014357:Trypsin / Q000378:metabolism
D000911:Antibodies, Monoclonal; D046911:Macromolecular Substances; D008565:Membrane Proteins; D011480:Protease Inhibitors; D006026:Glycoside Hydrolases; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D010447:Peptide Hydrolases; D014357:Trypsin