Nematode sperm are unusual amoeboid cells in which motility is not based on
actin, but instead on the major sperm protein (MSP) that polymerizes to form a
cytoskeleton constructed from intermeshed filaments. MSP is a dimeric molecule
that polymerizes 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 [1,2,3,4]. An about 120-amino acid domain similar to MSP has been
found in the following proteins:
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 α-helical coiled-coil combined with an extremly hydrophobic
membrane-attachment region .
Nicotiana plumbaginifolia VAP27, a VAP33 homologue. It interacts with the
resistance protein Cf9 .
Yeast inositol regulator SCS2, a VAP33 homologue. It is C-terminally
anchored to the endoplasmic reticulum .
The MSP polypeptide chain has an immunoglobulin-like fold based on a seven-stranded β sandwich measuring approximately 15 A x 20 A x 45 A and having
opposing three-stranded and four-stranded β sheets (see <PDB:1MSP>) .
The profile we developed covers the entire MSP domain.
PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and
distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives
(CC BY-NC-ND 4.0) License, see prosite_license.html.