Fig. 2. (A) Translated amino acid sequence of clone LL_MET (Periwinkle, encoding the protein Ll-MT) aligned with amino acid sequences of metallothioneins (MT) from other mollusc species: land snail Helix pomatia cadmium (Cd) MT (midgut-derived, GenBank accession number P33187) and copper (Cu) MT (accession number P55947); blue mussel Mytilus edulis 20-Ib (accession number S47576) and oyster Crassostrea virginica (accession number S17156). Conserved amino acids are highlighted in black. Gray highlights indicate residues that are shared between Ll-MT and at least two other sequences in the figure. The boxed residues at the C terminus comprise a highly conserved motif, Cys-X-Cys-X(3)-Cys-Thr-Gly-X(3)-Cys-X-Cys-X(3)-Cys-X-Cys-Lys, which categorizes Ll-MT into the mollusc family (family 2) of the MT classification system. (–) indicates an inserted gap. (B) Homology tree of MTs from selected invertebrate species. The percentage identities between the groups are indicated to the right of the forks. Sequences were aligned and the homology tree generated using the protein alignment matrix (PAM; Dayhoff et al., 1978) as employed in DNAman. The sequences were obtained from GenBank; accession numbers for species not listed in A are: lobster Homarus americanus (accession number A37039), mud crab Scylla serrata (accession number P02805), sea urchin Strongylocentrotus purpuratus (accession number P04734) and nematode Caenorhabditis elegans (accession number A34905).