Identification and functional analysis of the gene cluster for L-arabinose utilization in Corynebacterium glutamicum.
Corynebacterium glutamicum ATCC 31831 grew on l-arabinose as the sole carbon source at a specific growth rate that was twice that on d-glucose. The gene cluster responsible for l-arabinose utilization comprised a six-cistron transcriptional unit with a total length of 7.8 kb. Three l-arabinose-catabolizing genes, araA (encoding l-arabinose isomerase), araB (l-ribulokinase), and araD (l-ribulose-5-phosphate 4-epimerase), comprised the araBDA operon, upstream of which three other genes, araR (LacI-type transcriptional regulator), araE (l-arabinose transporter), and galM (putative aldose 1-epimerase), were present in the opposite direction. Inactivation of the araA, araB, or araD gene eliminated growth on l-arabinose, and each of the gene products was functionally homologous to its Escherichia coli counterpart. Moreover, compared to the wild-type strain, an araE disruptant exhibited a >80% decrease in the growth rate at a lower concentration of l-arabinose (3.6 g liter(-1)) but not at a higher concentration of l-arabinose (40 g liter(-1)). The expression of the araBDA operon and the araE gene was l-arabinose inducible and negatively regulated by the transcriptional regulator AraR. Disruption of araR eliminated the repression in the absence of l-arabinose. Expression of the regulon was not repressed by d-glucose, and simultaneous utilization of l-arabinose and d-glucose was observed in aerobically growing wild-type and araR deletion mutant cells. The regulatory mechanism of the l-arabinose regulon is, therefore, distinct from the carbon catabolite repression mechanism in other bacteria.
Research Institute of Innovative Technology for the Earth, Kyoto, Japan.
Hideo
H
Kawaguchi
Miho
M
Sasaki
Alain A
AA
Vertès
Masayuki
M
Inui
Hideaki
H
Yukawa
D000332:Aerobiosis; D001089:Arabinose / Q000378:metabolism*; D002238:Carbohydrate Epimerases / Q000235:genetics; D048230:Corynebacterium glutamicum / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005796:Genes; D005798:Genes, Bacterial; D005947:Glucose / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics; D053858:Metabolic Networks and Pathways / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D017422:Sequence Analysis, DNA; D017385:Sequence Homology
D004269:DNA, Bacterial; D026901:Membrane Transport Proteins; D001089:Arabinose; D002238:Carbohydrate Epimerases; C019646:aldose 1-epimerase; D005947:Glucose