Positive regulation of Bacillus subtilis ackA by CodY and CcpA: establishing a potential hierarchy in carbon flow.
Conversion of pyruvate to acetate via the phosphotransacetylase-acetate kinase pathway generates ATP and is a major overflow pathway under conditions of carbon and nitrogen excess. In Bacillus subtilis, this pathway is positively regulated by CcpA, a global regulator of carbon metabolism genes. Transcription of the acetate kinase gene (ackA) proved to be activated as well by a second global regulatory protein, CodY. Expression of an ackA-lacZ fusion was reduced in a codY mutant strain. CodY was found to bind in vitro to two sites in the ackA promoter region and to stimulate ackA transcription in a run-off transcription assay. This is the first known case of direct positive regulation by CodY. CodY and CcpA were found to bind to neighbouring sites and their effects were additive both in vivo and in vitro. Surprisingly, positive regulation by CodY, unlike repression, responded primarily to only one type of effector molecule. That is, branched-chain amino acids (BCAAs) served as more potent co-activators of CodY-dependent ackA transcription than did GTP. Given the roles of CcpA and CodY in regulating genes whose products determine the metabolic fate of pyruvate, these two proteins may act together to mediate a hierarchical conversion of pyruvate to its many potential products.
Shivers
Robert P
RP
Department of Molecular Biology and Microbiology, School of Medicine, Tufts University, Boston, MA, USA.
Dineen
Sean S
SS
Sonenshein
Abraham L
AL
D000084:Acetate Kinase / Q000235:genetics* / Q000378:metabolism; D000597:Amino Acids, Branched-Chain / Q000378:metabolism; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002244:Carbon / Q000378:metabolism*; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D019289:Pyruvic Acid / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D000597:Amino Acids, Branched-Chain; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; C069286:catabolite control proteins, bacteria; D002244:Carbon; D019289:Pyruvic Acid; D000084:Acetate Kinase; D003850:Deoxyribonuclease I