Molecular analysis of mxbD and mxbM, a putative sensor-regulator pair required for oxidation of methanol in Methylobacterium extorquens AM1.
Five genes are thought to be required for transcription of methanol oxidation genes in Methylobacterium strains. These putative regulatory genes include mxcQE, which encode a putative sensor-regulator pair, and mxbDM and mxaB, whose functions are less well-understood. In this study, mxbDM in Methylobacterium extorquens AM1 were shown to be required for expression of a xylE transcriptional fusion to the structural gene for the large subunit of methanol dehydrogenase (mxaF), confirming the role of these genes in transcriptional regulation of mxaF. The nucleotide sequence suggests that mxbD encodes a histidine protein kinase with two transmembrane domains and that mxbM encodes a DNA-binding response regulator. A xylE transcriptional fusion to the putative mxbD promoter showed low-level expression in wild-type cells grown on one-carbon (C1) compounds and no detectable expression in cells grown on succinate. Deletion analysis of this promoter construct showed that the region 229-129 bp upstream of the start of mxbD is required for expression. The expression of the mxbD-xylE fusion was examined in each of the five known regulatory mutant classes. xylE expression was reduced to non-detectable levels in MxcQ and MxcE mutants, but was not affected in the other regulatory mutants or in non-regulatory mutants defective in methanol oxidation. These results suggest a regulatory hierarchy in which the sensor-regulator pair MxcQE control expression of the sensor-regulator pair MxbDM, and MxbDM in turn control expression of a number of genes involved in methanol oxidation.
Springer
Amy L
AL
Department of Chemical Engineering, Box 351750, University of Washington, Seattle, WA 98195-1750, USA.
Morris
Christina J
CJ
Department of Chemical Engineering, Box 351750, University of Washington, Seattle, WA 98195-1750, USA.
Lidstrom
Mary E
ME
Department of Microbiology, Box 357242, University of Washington, Seattle, WA 98195-1750, USA.|Department of Chemical Engineering, Box 351750, University of Washington, Seattle, WA 98195-1750, USA.
D000429:Alcohol Oxidoreductases / Q000096:biosynthesis / Q000235:genetics*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D050557:Catechol 2,3-Dioxygenase; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D049308:Dioxygenases; D004734:Energy Metabolism / Q000235:genetics; D004790:Enzyme Induction; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005809:Genes, Regulator; D006088:Gram-Negative Aerobic Bacteria / Q000235:genetics* / Q000378:metabolism; D000432:Methanol / Q000378:metabolism*; D008969:Molecular Sequence Data; D010105:Oxygenases / Q000096:biosynthesis / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics* / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D013379:Substrate Specificity; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C106640:MxbM protein, Methylobacterium extorquens; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D000429:Alcohol Oxidoreductases; C019641:alcohol dehydrogenase (acceptor); D010105:Oxygenases; D049308:Dioxygenases; D050557:Catechol 2,3-Dioxygenase; D011494:Protein Kinases; C106639:MxbD protein, Methylobacterium extorquens; D000432:Methanol