Methylmalonyl-CoA mutase encoding gene of Sinorhizobium meliloti.
A cluster of genes on megaplasmid pRmeSU47b, bhbA-D, is required for growth on the polyhydroxyalkanoate degradation pathway intermediates 3-hydroxybutyrate and acetoacetate as sole carbon source. DNA sequence analysis of the bhbA gene indicated that it encoded a protein of 712 amino acids (aa) (78kDa) which appeared to be a homodimeric methylmalonyl-CoA mutase enzyme (EC 5.4.99.2). Cell-free extract of a bhbA::Tn5 mutant was devoid of methylmalonyl-CoA mutase activity, thus confirming the identity of the bhbA-encoded enzyme. The reason for the requirement of methylmalonyl-CoA mutase activity for operation of the polyhydroxyalkanoate degradation pathway is not immediately apparent. Situated immediately upstream of bhbA, in the same orientation, is a gene which is predicted to encode a protein that exhibits remarkable sequence similarity to the alpha subunit of propionyl-CoA carboxylase (EC 6.4.1.3). A mutation in this gene did not affect ability to grow on 3-hydroxybutyrate as sole carbon source. Downstream of, and oriented towards bhbA, was identified a member of the GNTR class of transcriptional regulator-encoding genes. It is not yet known whether this regulatory protein is directly involved in modulation of bhbA expression.
Charles
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TC
Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, Que. H9X 3V9, Canada. tcharles@uwaterloo.ca
Aneja
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D020155:3-Hydroxybutyric Acid / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D043586:Methylmalonyl-CoA Decarboxylase; D008765:Methylmalonyl-CoA Mutase / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D017422:Sequence Analysis, DNA; D016962:Sinorhizobium meliloti / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
D004251:DNA Transposable Elements; D002262:Carboxy-Lyases; D008765:Methylmalonyl-CoA Mutase; D043586:Methylmalonyl-CoA Decarboxylase; D020155:3-Hydroxybutyric Acid