A mouse acrosomal cortical matrix protein, MC41, has ZP2-binding activity and forms a complex with a 75-kDa serine protease.
Sperm with a large acrosome such as that of guinea pigs and hamsters have a subdomain structure in the anterior acrosome, but the mouse acrosome looks homogeneous and its matrix has not been precisely analyzed. The intra-acrosomal protein MC41 is localized in the cortical region of the mouse anterior acrosome, suggesting a subdomain structure in the mouse acrosome. Thus, the present study was undertaken to analyze the mouse acrosomal matrix using an anti-MC41 antibody. When mouse sperm were treated with 2% Triton X-100, Triton-insoluble matrix components remained in the acrosomal cortical region. Immunogold for MC41 labeled the Triton X-100 and high-salt-insoluble matrix components, demonstrating that MC41 is a subdomain-specific acrosomal matrix protein. We further examined interactions of MC41 with acrosomal proteases and zona proteins. A serine protease of 75 kDa was associated with MC41 under low-salt conditions, presumably forming a complex. Far Western blotting technique indicated that MC41 bound to both ZP2 and ZP2(f) in the presence of high-salt-soluble sperm proteins. In acrosome-reacting sperm, MC41 was present on the hybrid vesicles formed by the fusion of the plasma and outer acrosomal membranes. Presumably, MC41 has a significant role in secondary sperm-zona binding during the acrosomal reaction.
Tanii
I
I
Department of Anatomy and Reproductive Cell Biology, Miyazaki Medical College, Kihara 5200, Kiyotake, Miyazaki, 889-1692, Japan. itanii@post1.miyazaki-med.ac.jp
Oh-oka
T
T
Yoshinaga
K
K
Toshimori
K
K
D020101:Acrosome Reaction; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D000941:Antigens / Q000737:chemistry* / Q000378:metabolism*; D015153:Blotting, Western; D003902:Detergents / Q000494:pharmacology; D004527:Egg Proteins / Q000378:metabolism*; D005260:Female; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D017830:Octoxynol / Q000494:pharmacology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface; D012697:Serine Endopeptidases / Q000378:metabolism*; D013094:Spermatozoa / Q000378:metabolism / Q000648:ultrastructure; D015044:Zona Pellucida / Q000378:metabolism / Q000648:ultrastructure; D000072216:Zona Pellucida Glycoproteins
D000911:Antibodies, Monoclonal; D000941:Antigens; D003902:Detergents; D004527:Egg Proteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins; C000606520:Zp2 protein, mouse; C403408:acrin 2; D017830:Octoxynol; D012697:Serine Endopeptidases