Figure 6.

A comparison of the precursor sequences of two ω-conotoxins, Gvia (top sequence) and Mviia (bottom sequence) from Conus geographus and Conus magus, respectively. Both of these toxins block the N-type voltage-gated calcium channel and compete with each other for binding. The entire precursor sequence is shown. The red amino acids comprise the signal sequence, whereas the solid arrow indicates the proteolytic site which generates the mature toxin. The mature toxin region is shown in capital letters, and the cysteine residues involved in disulfide bonding are shown bold. All loci where the two sequences differ are indicated by asterisks. It is notable that although the signal sequences are entirely identical, the vast majority of the non-Cys amino acids of mature ω-conotoxin Gvia are different from the corresponding ω-conotoxin Mviia residues; in contrast, the Cys residues in this region are completely conserved.