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Control of methionine metabolism by the SahR transcriptional regulator in P roteobacteria
Author(s) -
Novichkov Pavel S.,
Li Xiaoqing,
Kuehl Jennifer V.,
Deutschbauer Adam M.,
Arkin Adam P.,
Price Morgan N.,
Rodionov Dmitry A.
Publication year - 2014
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12273
Subject(s) - regulon , biology , biochemistry , sulfur metabolism , transcriptional regulation , regulator , methionine , transcription factor , metabolism , amino acid , gene
Summary Sulphur is an essential element in the metabolism. The sulphur‐containing amino acid methionine is a metabolic precursor for S ‐adenosylmethionine ( SAM ), which serves as a coenzyme for ubiquitous methyltrtansferases. Recycling of organic sulphur compounds, e.g. via the SAM cycle, is an important metabolic process that needs to be tightly regulated. Knowledge about transcriptional regulation of these processes is still limited for many free‐living bacteria. We identified a novel transcription factor SahR from the ArsR family that controls the SAM cycle genes in diverse microorganisms from soil and aquatic ecosystems. By using comparative genomics, we predicted SahR ‐binding DNA motifs and reconstructed SahR regulons in the genomes of 62 P roteobacteria. The conserved core of SahR regulons includes all enzymes required for the SAM cycle: the SAH hydrolase AhcY , the methionine biosynthesis enzymes MetE / MetH and MetF , and the SAM synthetase MetK . By using a combination of experimental techniques, we validated the SahR regulon in the sulphate‐reducing D eltaproteobacterium D esulfovibrio alaskensis . SahR functions as a negative regulator that responds to the S ‐adenosylhomocysteine ( SAH ). The elevated SAH level in the cell dissociates SahR from its DNA operators and induces the expression of SAM cycle genes. The effector‐sensing domain in SahR is related to SAM ‐dependent methylases that are able to tightly bind SAH . SahR represents a novel type of transcriptional regulators for the control of sulphur amino acid metabolism.