Table 1. Diagnostic characteristics of MT subfamilies 7a and 7b.

MT subfamily	Cys residues in CC or CCC clusters	Elementary sequence motifs	Lys next to Cys residues	Fold induction by Cd and Cu**
7a	Most	C2X6,most common; CKCXXCXCCK*	Minority	Cd>Cu
7b	Essentially none	CKCXXCKC	Strong majority	Cd<Cu

C, K and X = cysteine, lysine and any amino acid other than C, respectively.

^*Consensus sequence. In subfamily 7a this motif is present exclusively at C-termini of type 2 submodules, which in turn exclusively constitute the C-termini of modules.

^**To the extent reported so far: MTT1 [20]; this work); MTT3 and MTT5 (this work); TpigMT-1 and TpigMT-2 [19]; TpMT1 and TpMT2 [18]; MTT2 and MTT4 (L-F Feng and W. Miao, personal communication).