Mammalian fertilization: the strange case of sperm protein 56.

Department of Developmental and Regenerative Biology, Mount Sinai School of Medicine, One Gustave L Levy Place, New York, NY 10029-6574, USA. paul.wassarman@mssm.edu

BioEssays : news and reviews in molecular, cellular and developmental biology 2009 Feb

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During mammalian fertilization sperm bind to the egg's zona pellucida (ZP) after undergoing capacitation. Capacitated mouse sperm bind to mZP3 (one of three ZP glycoproteins), undergo the acrosome reaction, penetrate the ZP, and fuse with egg plasma membrane. Sperm protein 56 (sp56), a member of the C3/C4 superfamily of binding proteins, was identified nearly 20 years ago as a binding partner for mZP3 by photoaffinity cross-linking of acrosome-intact sperm. However, subsequent research revealed that sp56 is a component of the sperm's acrosomal matrix and, for sperm with an intact acrosome, should be unavailable for binding to mZP3. Recently, this dilemma was resolved when it was recognized that some acrosomal matrix (AM) proteins, including sp56, are released to the sperm surface during capacitation. This may explain why uncapacitated mammalian sperm are unable to bind to the unfertilized egg ZP.

Citation

Paul M Wassarman. Mammalian fertilization: the strange case of sperm protein 56. BioEssays : news and reviews in molecular, cellular and developmental biology. 2009 Feb;31(2):153-8