1.C.15 The Whipworm Stichosome Porin (WSP) Family
The human parasitic nematode, Trichuris trichiura (whipworm), infects about 20% of the world&146;s population, causing growth defects and impaired cognition. T. muris is the equivalent mouse parasite. A characteristic stichosome encloses much of the worm, and the major protein of stichosome extracts is WSP, a protein of 40-100 kDa which is capable of inducing pores in planar lipid bilayers. It consists of 9 (TT50) to 17 (TT95) tandemly arranged domains of 50-51 amino acyl residues in which cysteine spacing is highly conserved. This domain is called the 'WAP-type' four disulfide core domain. These repeats are found in a variety of proteins including the ovulatory protein-2 precursor (gbU67854) and secretory leukocyte protease inhibitor (spP97430). There is an N-terminal 23 hydrophobic amino acid signal sequence used for secretion.
Maintenance of attachment to the host gut requires continual invasion of new epithelia due to continuous sloughing of the gut wall. WSP appears to facilitate attachment and maintenance of the parasite in the gut, presumably by facilitating transport of small molecules (ions) across the epithelial membrane.