title: Paralogous cAMP receptor proteins in Mycobacterium smegmatis show biochemical and functional divergence.
abstract: The cyclic AMP receptor protein (CRP) family of transcription factors consists of global regulators of bacterial gene expression. Here, we identify two paralogous CRPs in the genome of Mycobacterium smegmatis that have 78% identical sequences and characterize them biochemically and functionally. The two proteins (MSMEG_0539 and MSMEG_6189) show differences in cAMP binding affinity, trypsin sensitivity, and binding to a CRP site that we have identified upstream of the msmeg_3781 gene. MSMEG_6189 binds to the CRP site readily in the absence of cAMP, while MSMEG_0539 binds in the presence of cAMP, albeit weakly. msmeg_6189 appears to be an essential gene, while the Δmsmeg_0539 strain was readily obtained. Using promoter-reporter constructs, we show that msmeg_3781 is regulated by CRP binding, and its transcription is repressed by MSMEG_6189. Our results are the first to characterize two paralogous and functional CRPs in a single bacterial genome. This gene duplication event has subsequently led to the evolution of two proteins whose biochemical differences translate to differential gene regulation, thus catering to the specific needs of the organism.
authors.affiliation: Department of Molecular Reproduction, Development and Genetics and ‡Department of Microbiology and Cell Biology, Indian Institute of Science , Bangalore 560012, India.
authors.forename: Ritu
authors.initials: R
authors.lastname: Sharma
authors.forename: Anisha
authors.initials: A
authors.lastname: Zaveri
authors.forename: Jayashree
authors.initials: J
authors.lastname: Gopalakrishnapai
authors.forename: Thiruneelakantan
authors.initials: T
authors.lastname: Srinath
authors.forename: Srinath
authors.initials: S
authors.lastname: Thiruneelakantan
authors.forename: Umesh
authors.initials: U
authors.lastname: Varshney
authors.forename: Sandhya S
authors.initials: SS
authors.lastname: Visweswariah
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D002373:Cyclic AMP Receptor Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020440:Gene Duplication; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D059748:Proteolysis; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D020218:Response Elements; D016415:Sequence Alignment; D017385:Sequence Homology; D014357:Trypsin / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D000242:Cyclic AMP; D014357:Trypsin