L-sorbose reductase and its transcriptional regulator involved in L-sorbose utilization of Gluconobacter frateurii.
Upstream of the gene for flavin adenine dinucleotide (FAD)-dependent D-sorbitol dehydrogenase (SLDH), sldSLC, a putative transcriptional regulator was found in Gluconobacter frateurii THD32 (NBRC 101656). In this study, the whole sboR gene and the adjacent gene, sboA, were cloned and analyzed. sboR mutation did not affect FAD-SLDH activity in the membrane fractions. The SboA enzyme expressed and purified from an Escherichia coli transformant showed NADPH-dependent L-sorbose reductase (NADPH-SR) activity, and the enzyme was different from the NADPH-SR previously reported for Gluconobacter suboxydans IFO 3291 in molecular size and amino acid sequence. A mutant defective in sboA showed significantly reduced growth on L-sorbose, indicating that the SboA enzyme is required for efficient growth on L-sorbose. The sboR mutant grew on L-sorbose even better than the wild-type strain did, and higher NADPH-SR activity was detected in cytoplasm fractions. Reverse transcription-PCR experiments indicated that sboRA comprises an operon. These data suggest that sboR is involved in the repression of sboA, but not in the induction of sldSLC, on D-sorbitol and that another activator is required for the induction of these genes by D-sorbitol or L-sorbose.
Soemphol
Wichai
W
Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan.
Toyama
Hirohide
H
Moonmangmee
Duangtip
D
Adachi
Osao
O
Matsushita
Kazunobu
K
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015139:Blotting, Southern; D004591:Electrophoresis, Polyacrylamide Gel; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D005798:Genes, Bacterial; D020576:Gluconobacter / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D007064:L-Iditol 2-Dehydrogenase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013013:Sorbose / Q000378:metabolism*; D013401:Sugar Alcohol Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D005182:Flavin-Adenine Dinucleotide; D013401:Sugar Alcohol Dehydrogenases; D007064:L-Iditol 2-Dehydrogenase; C506437:sorbose reductase; D013013:Sorbose