Specificity of binding of zona pellucida glycoproteins to sperm proacrosin and related proteins.
A major regulatory site for species specificity of fertilization in mammals lies at the level of sperm binding to the zona pellucida. This implies a high degree of complementarity between gamete receptor molecules. One putative receptor molecule on spermatozoa is proacrosin/acrosin which binds to zona pellucida glycoproteins (ZPGPs) non-enzymically and with high affinity. The mechanism of recognition involves polysulphate groups in a particular stereochemical orientation and it has been suggested that this may contribute to species specificity of sperm-egg binding. In the present work this hypothesis has been tested by challenging 125I-labelled ZPGPs from pig, cow, and hamster eggs to recognize heterologous sperm proacrosins as well as a variety of sequence-related and unrelated proteins. Results show that pig and cow 125I-ZPGPs bind readily to boar, ram, and bull proacrosin but do not recognize guinea-pig proacrosin or any of the polysulphate binding proteins from rat, hamster, or mouse spermatozoa. Hamster 125I-ZPGPs also recognise boar, ram, and bull proacrosin as well as a range of unidentified proteins in pH3 extracts of hamster, rat, and mouse spermatozoa. The binding of ZPGPs to a variety of proteins not related to proacrosin is strongest to those with a high content of basic residues (i.e., pI > 8.5), although the secondary folding of the target protein is of major importance as boar proacrosin (pI 6.75) has the highest binding capacity of all proteins tested. Cross-reaction of ZPGP probes was not observed to guinea-pig proacrosin, suggesting that in this species the conformation of the protein is different to other sperm proacrosins.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Biochemistry, Institute of Animal Physiology and Genetics Research, AFRC, Babraham, Cambridge, United Kingdom.
R M
RM
Williams
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R
Jones
D000176:Acrosin / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D004527:Egg Proteins; D004792:Enzyme Precursors / Q000378:metabolism*; D005260:Female; D006041:Goats; D006168:Guinea Pigs; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D011956:Receptors, Cell Surface; D012756:Sheep; D013045:Species Specificity; D013094:Spermatozoa; D013552:Swine; D015044:Zona Pellucida; D000072216:Zona Pellucida Glycoproteins
D004527:Egg Proteins; D004792:Enzyme Precursors; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins; C022438:proacrosin; D000176:Acrosin