Divergent M- and O-superfamily peptides from venom of fish-hunting Conus parius

Six novel peptides from the piscivorous cone snail, Conus parius were purified by reverse-phase HPLC fractionation of crude venom. With the use of matrix-assisted laser desorption ionization mass spectrometry and standard Edman sequencing methods, the peptides were characterized. Two peptides were identified as members of the m-2 and m-4 branches of the M-superfamily and were designated as pr3a and pr3b, while four peptides were identified as members of the O-superfamily and were designated as pr6a, pr6b, pr6c and pr6d. Peptide pr3a differs from the majority of the M-superfamily peptides in the presence of two prolines, which are not modified to 4-trans-hydroxyproline. In peptide pr3b, five amino acids out of the 16 non-cysteine residues are identical with those of mu-GIIIA and mu-PIIIA, suggesting that pr3b may be a divergent mu-conotoxin. Peptide pr6a is notable because of its extreme hydrophobicity. Peptide pr6c has three prolines that are unhydroxylated. Peptides pr6b and pr6d differ from the previously characterized O-superfamily peptides in the presence of an extended N-terminus consisting of six amino acids. Peptides pr3a, pr3b, pr6a and pr6b were demonstrated to be biologically active when injected intraperitoneally in fish. The identification and characterization of these peptides in venom of a fish-hunting species establish the divergence of gene products and their patterns of post-translational modification within superfamilies in a single Conus species.