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Appl. Environ. Microbiol., Apr 1995, 1279-1289, Vol 61, No. 4
DL Daubaras, CD Hershberger, K Kitano and AM Chakrabarty
Burkholderia cepacia AC1100 utilizes 2,4,5-trichlorophenoxyacetic acid
(2,4,5-T) as a sole source of carbon and energy. PT88 is a chromosomal
deletion mutant of B. cepacia AC1100 and is unable to grow on 2,4,5-T. The
nucleotide sequence of a 5.5-kb chromosomal fragment from B. cepacia AC1100
which complemented PT88 for growth on 2,4,5-T was determined. The sequence
revealed the presence of six open reading frames, designated ORF1 to ORF6.
Five polypeptides were produced when this DNA region was under control of
the T7 promoter in Escherichia coli; however, no polypeptide was produced
from the fourth open reading frame, ORF4. Homology searches of protein
sequence databases were performed to determine if the proteins involved in
2,4,5-T metabolism were similar to other biodegradative enzymes. In
addition, complementation studies were used to determine which genes were
essential for the metabolism of 2,4,5-T. The first gene of the cluster,
ORF1, encoded a 37-kDa polypeptide which was essential for complementation
of PT88 and showed significant homology to putative
trans-chlorodienelactone isomerases. The next gene, ORF2, was necessary for
complementation and encoded a 47-kDa protein which showed homology to
glutathione reductases. ORF3 was not essential for complementation;
however, both the 23-kDa protein encoded by ORF3 and the predicted amino
acid sequence of ORF4 showed homology to glutathione S- transferases. ORF5,
which encoded an 11-kDa polypeptide, was essential for growth on 2,4,5-T,
but the amino acid sequence did not show homology to those of any known
proteins. The last gene of the cluster, ORF6, was necessary for
complementation of PT88, and the 32-kDa protein encoded by this gene showed
homology to catechol and chlorocatechol-1,2- dioxygenases.
Copyright © 1995, American Society for Microbiology
Sequence analysis of a gene cluster involved in metabolism of 2,4,5- trichlorophenoxyacetic acid by Burkholderia cepacia AC1100
Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago 60612, USA.
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