tfdA-like genes in 2,4-dichlorophenoxyacetic acid-degrading bacteria belonging to the Bradyrhizobium-Agromonas-Nitrobacter-Afipia cluster in alpha-Proteobacteria.
The 2,4-dichlorophenoxyacetate (2,4-D)/alpha-ketoglutarate dioxygenase gene (tfdA) homolog designated tfdAalpha was cloned and characterized from 2,4-D-degrading bacterial strain RD5-C2. This Japanese upland soil isolate belongs to the Bradyrhizobium-Agromonas-Nitrobacter-Afipia cluster in the alpha subdivision of the class Proteobacteria on the basis of its 16S ribosomal DNA sequence. Sequence analysis showed 56 to 60% identity of tfdAalpha to representative tfdA genes. A MalE-TfdAalpha fusion protein expressed in Escherichia coli exhibited about 10 times greater activity for phenoxyacetate than 2,4-D in an alpha-ketoglutarate- and Fe(II)-dependent reaction. The deduced amino acid sequence of TfdAalpha revealed a conserved His-X-Asp-X(146)-His-X(14)-Arg motif characteristic of the active site of group II alpha-ketoglutarate-dependent dioxygenases. The tfdAalpha genes were also detected in 2,4-D-degrading alpha-Proteobacteria previously isolated from pristine environments in Hawaii and in Saskatchewan, Canada (Y. Kamagata, R. R. Fulthorpe, K. Tamura, H. Takami, L. J. Forney, and J. M. Tiedje, Appl. Environ. Microbiol. 63:2266-2272, 1997). These findings indicate that the tfdA genes in beta- and gamma-Proteobacteria and the tfdAalpha genes in alpha-Proteobacteria arose by divergent evolution from a common ancestor.
Itoh
Kazuhito
K
Faculty of Life and Environmental Science, Shimane University, Matsue, Shimane 690-8504, Japan. itohkz@life.shimane-u.ac.jp
Kanda
Rie
R
Sumita
Yoko
Y
Kim
Hongik
H
Kamagata
Yoichi
Y
Suyama
Kousuke
K
Yamamoto
Hiroki
H
Hausinger
Robert P
RP
Tiedje
James M
JM
D015084:2,4-Dichlorophenoxyacetic Acid / Q000378:metabolism*; D020622:Afipia / Q000378:metabolism*; D020561:Alphaproteobacteria / Q000145:classification / Q000378:metabolism*; D000595:Amino Acid Sequence; D020369:Bradyrhizobium / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D008969:Molecular Sequence Data; D009576:Nitrobacter / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D011993:Recombinant Fusion Proteins; D015084:2,4-Dichlorophenoxyacetic Acid; D006899:Mixed Function Oxygenases; C084087:2,4-dichlorophenoxyacetate-alpha-ketoglutarate dioxygenase