Dynamics of the membrane system

Abstract

Proteins in the sperm plasma membrane are modified when the spermatozoa pass through the extracellular matrix surrounding the cumulus cells. Thus far, I have investigated the IgSF proteins basigin, CE9, and MC31 in this regard (Fig. 8.1).

Mouse basigin (expressed in mice with the Ok blood group) (Igakura et al. 1998; Kuno et al. 1998; Miyauchi et al. 1990) is homologous to the human extracellular matrix metalloproteinase inducer (EMMPRIN), HT-7, CD147, 5A11, M6 (leukocye- activation antigen), 5F7, tumor cell-derived collagenase factor (TCSF), gp42, neurothelin, and the MRC OX-47 T-cell-activation antigen. The rat homolog ofbasigin is CE9 (de la Luna et al. 1999; Petruszak et al. 1991), which is identical to MC31 (Toshimori et al. 1992a; Wakayama et al. 2000). Mouse bsg is localized at locus 42.2 on chromosome 10, and human EMMPRIN is localized on chromosome 19p13.3.

Molecular structure of BSG and CE9/MC31: Basigin and CE9 (MC31) are predicted to be single-pass type-1 glycoproteins that comprise 269 amino acids and contain three potential N-glycosylation sites. Basigin is composed of 269 amino acids, and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and immunoblotting analyses have revealed its molecular size to range from 35 to 60 kDa. The extracellular domain is composed of 187 amino acids and contains two Ig-related domains. The basigin-encoding gene BSG contains seven exons with a total length of 1.8 kb. Its molecular structure, as predicted on the basis of genetic analysis, is shown in Fig. 8.1.