A mutant metallothionein which has inverse fragment composition exhibits high cadmium-binding ability.
In order to investigate the role of the alpha-fragment of metallothionein (MT) in metal-binding, two mutant MTs, beta Ala alpha Cys- and alpha Cys beta Cys-mutant MTs, expressed in Escherichia coli were analyzed for their metal-binding ability. A mutant MT where all of the cysteine residues in the beta-fragment of MT were substituted by alanine residues and another mutant MT that had the inverse fragment composition (alpha-beta, i.e., beta-alpha in wild-type MT) were designated as the beta Ala alpha Cys and the alpha Cys beta Cys-mutant MT's, respectively. Both expressed Cd-binding mutant MTs were identified by amino acid analyses. From their metal-binding capacities, the two mutant MTs exhibited higher Cd-binding abilities than wild-type MT. The results suggested that the alpha-fragment plays a key role in the Cd-binding of MT, and that the metal-binding tightness of MT is dependent on the metal-binding ability of a prior fragment in MT.
Yamaguchi
R
R
Department of Environmental Medicine and Informatics, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Japan.
Kurasaki
M
M
Kojima
Y
Y
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence / Q000502:physiology; D001665:Binding Sites; D002104:Cadmium / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D004926:Escherichia coli; D006801:Humans; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D017354:Point Mutation; D011994:Recombinant Proteins
D011994:Recombinant Proteins; D002104:Cadmium; D008668:Metallothionein; D003545:Cysteine; D000409:Alanine