Identification of a copper-binding metallothionein in pathogenic mycobacteria.
A screen of a genomic library from Mycobacterium tuberculosis (Mtb) identified a small, unannotated open reading frame (MT0196) that encodes a 4.9-kDa, cysteine-rich protein. Despite extensive nucleotide divergence, the amino acid sequence is highly conserved among mycobacteria that are pathogenic in vertebrate hosts. We synthesized the protein and found that it preferentially binds up to six Cu(I) ions in a solvent-shielded core. Copper, cadmium and compounds that generate nitric oxide or superoxide induced the gene's expression in Mtb up to 1,000-fold above normal expression. The native protein bound copper within Mtb and partially protected Mtb from copper toxicity. We propose that the product of the MT0196 gene be named mycobacterial metallothionein (MymT). To our knowledge, MymT is the first metallothionein of a Gram-positive bacterium with a demonstrated function.
Gold
Ben
B
Department of Microbiology and Immunology, Weill Cornell Medical College, 1300 York Avenue, New York, New York 10065, USA.
Deng
Haiteng
H
Bryk
Ruslana
R
Vargas
Diana
D
Eliezer
David
D
Roberts
Julia
J
Jiang
Xiuju
X
Nathan
Carl
C
D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D003300:Copper / Q000737:chemistry*; D015964:Gene Expression Regulation, Bacterial; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment
D003300:Copper; D008668:Metallothionein