ShK proteins are named after the Stichodactyla helianthus potassium (K) channel-blocking toxin (1). Previously, members of this gene family had been discovered by the Maizels Lab in Toxocara canis, as chimeric constructs fused both to the phosphatidylethanolamine-binding protein module in the secreted TES-26 (2), and to multiple secreted TES-120 mucins (3). They have a conserved set of 6 cysteine residues, hence the earlier names of NC6 (Nematode Cys-6) and SXC (SiX Cysteine).
A homologue from the filarial nematode Brugia malayi is an inhibitor of T cell activation (4).
(1) Tudor, J.E., Pennington, M.W. and Norton, R.S. (1998). Ionisation behaviour and solution properties of the potassium-channel blocker ShK toxin. Eur J Biochem 251(1-2): 133-141.
(2) Gems, D.H., Ferguson, C.J., Robertson, B.D., Nieves, R., Page, A.P., Blaxter, M.L. and Maizels, R.M. (1995). An abundant, trans-spliced mRNA from Toxocara canis infective larvae encodes a 26 kDa protein with homology to phosphatidylethanolamine binding proteins. Journal of Biological Chemistry 270: 18517-18522.
(3) Gems, D.H. and Maizels, R.M. (1996). An abundantly expressed mucin-like protein from Toxocara canis infective larvae: the precursor of the larval surface coat glycoproteins. Proceedings of the National Academy of Sciences USA 93: 1665-1670.
(4) Chhabra, S., Chang, S.C., Nguyen, H.M., Huq, R., Tanner, M.R., Londono, L.M., Estrada, R., Dhawan, V., Chauhan, S., Upadhyay, S.K., Gindin, M., Hotez, P.J., Valenzuela, J.G., Mohanty, B., Swarbrick, J.D., Wulff, H., Iadonato, S.P., Gutman, G.A., Beeton, C., Pennington, M.W., Norton, R.S. and Chandy, K.G. (2014). Kv1.3 channel-blocking immunomodulatory peptides from parasitic worms: implications for autoimmune diseases. FASEB J 28(9): 3952-3964. http://www.ncbi.nlm.nih.gov/pubmed/24891519