Significance of alpha-fragment of metallothionein in cadmium binding.
In order to evaluate the significance of alpha- and beta-fragments of metallothionein with regard to Cd binding in biosynthetic processes, the Cd-binding ability of four mutant metallothioneins was examined using the Escherichia coli expression system. The features of the mutant metallothioneins were proteins in which cysteine residues in the alpha- or beta-fragment were replaced with alanine residues, or that the sequential order of the fragments was altered. The expressed mutant metallothioneins having an intact alpha-fragment showed the constructive abilities of the Cd-thiolate cluster. On the other hand, mutant metallothionein having an alpha-fragment lacking metal-binding sites exhibited no Cd-binding ability. The condition for maintaining the Cd-binding capability of metallothionein was that the alpha-fragment remains intact irrespective of the sequential order of the two fragments. The alpha-fragment is an indispensable component in metal-binding processes of Cd-metallothionein.
Kurasaki
M
M
Department of Environmental Medicine and Informatics, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Japan.
Yamaguchi
R
R
Linde Arias
A R
AR
Okabe
M
M
Kojima
Y
Y
D000595:Amino Acid Sequence; D001665:Binding Sites; D002104:Cadmium / Q000378:metabolism*; D004926:Escherichia coli; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
D010446:Peptide Fragments; D002104:Cadmium; D008668:Metallothionein