The N-terminal Cytoplasmic MSP (Major Sperm Protein) Domain

The N-terminal cytoplasmic MSP (major sperm protein) domain of VAP-B consistes of 125 amino acids (aa), and a coiled-coil domain (CCD) of ~50 aa. Proline 56 resides within a highly conserved sequence of 16 aa in the MSP
domain in a cis-peptide bond conformation, therefore, the serine substitution induces its cis-to-trans isomerization. By using set of truncated mutants of VAP-B, we found that the oligomerization of the wild-type VAP-B is independent of its MSP domain.