Structure of a novel P-superfamily spasmodic conotoxin reveals an inhibitory cystine knot motif

Conotoxin gm9a, a putative 27-residue polypeptide encoded by Conus gloriamaris, was recently identified as a homologue of the "spasmodic peptide", tx9a, isolated from the venom of the mollusk-hunting cone shell Conus textile (Lirazan, M. B., Hooper, D., Corpuz, G. P., Ramilo, C. A., Bandyopadhyay, P., Cruz, L. J., and Olivera, B. M. (2000) Biochemistry 39, 1583-1588). The C. gloriamaris spasmodic peptide has been synthesized, and the refolded polypeptide was shown to be biologically active using a mouse bioassay.