Fig. 1.

(A) Amino acid sequence alignment of recombinant SpMTA and SpMTB. Note that the N-term Gly–Ser residues derive from the GST-fusion system used for recombinant synthesis and purification. (B) 3D structures of Cd₄-αSpMTA (top) and Cd₃-βSpMTA (bottom) generated from PDB files 1QJK and 1QJL, respectively, with VMD software (http://www.ks.uiuc.edu/Research/vmd/) [Humphrey W, Dalke A, Schulten K. VMD – visual molecular dynamics. J. Molec. Graphics 1996;14:33–38]. Color code: random coil, silver; turn, cyan; extended beta, orange; Cd(II) ions, purple; Cys residue backbone and Cys-Cd connectivities, yellow. N-term and C-term ends of SpMTA sequence are indicated, and an arrow marks the position of the insertion of a Thr residue in SpMTB. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)