Major sperm protein (MSP) domain (IPR000535)

Short name: MSP_dom

Overlapping homologous superfamilies

Domain relationships



Nematode sperm are unusual amoeboid cells in which motility is not based on actin, but instead on the major sperm protein (MSP). MSP is a dimeric molecule that polymerises to form non-polar filaments constructed from two helical subfilaments that wind round one another. The filaments then assemble into larger macromolecular assemblies called fibre complexes. MSP is a small (~14 kDa) basic protein typically encoded by a multigene family of up to 28 members [PMID: 8913307, PMID: 12051923, PMID: 9878374, PMID: 9641981]. An about 120-amino acid domain similar to MSP has been found in other proteins, including:

  • Animal Vesicle-Associated Membrane Protein-associated (VAMP-associated) protein family of 33 kDa (VAP33). VAP33 is required for neurotransmitter release. It binds to the v-SNARE synaptobrevin/VAMP which is associated with vesicle fusion. VAP33 has a two-domain structure with its N terminus being highly homologous to MSP, whereas its C terminus is based on a putative alpha-helical coiled-coil combined with an extremly hydrophobic membrane-attachment region [PMID: 9920726].
  • Nicotiana plumbaginifolia VAP27, a VAP33 homologue. It interacts with the resistance protein Cf9 [PMID: 10733941].
  • Yeast inositol regulator SCS2, a VAP33 homologue. It is C-terminally anchored to the endoplasmic reticulum [PMID: 9537365].

The MSP polypeptide chain has an immunoglobulin-like fold based on a seven- stranded beta sandwich measuring approximately 15 A x 20 A x 45 A and having opposing three-stranded and four-stranded beta sheets [PMID: 8913307].

This entry represents the MSP domain.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE profiles