I-conotoxins in vermivorous species of the West Atlantic: peptide sr11a from Conus spurius.

Peptide sr11a was purified from the venom of Conus spurius, a vermivorous cone snail collected in the Yucatan Channel, in the Western Atlantic. Its primary structure was determined by automatic Edman degradation after reduction and alkylation. Its molecular mass, as determined by MALDI-TOF mass spectrometry (average mass 3650.77 Da), confirmed the chemical data (calculated average mass, 3651.13 Da). The sequence of peptide sr11a (CRTEGMSCgamma gamma NQQCCWRSCCRGECEAPCRFGP&; gamma, gamma-carboxy-Glu; &, amidated C-terminus) shows eight Cys residues arranged in the pattern that defines the I-superfamily of conotoxins. Peptide sr11a contains two gamma-carboxy-Glu residues, a post-translational modification that has been found in other I-conotoxins from species that live in the West Pacific: r11e from the piscivorous Conus radiatus, and kappa-BtX from the vermivorous Conus betulinus. Peptide sr11a is the eighth I-conotoxin isolated from a Conus venom and the first I-conotoxin from a species from the Western Atlantic. Peptide sr11a produced stiffening of body, limbs and tail when injected intracranially into mice.