Contributions of environmental signals and conserved residues to the functions of carbon storage regulator A of Borrelia burgdorferi (csrABb). ncbi.nlm.nih.gov/pubmed/23753623 nfect Immun. 2013 Jun 10. [Epub ahead of print] Karna SL, Prabhu RG, Lin YH, Miller CL, Seshu J. Source South Texas Center for Emerging Infectious Diseases, Center of Excellence in Infection Genomics and Department of Biology, The University of Texas at San Antonio, TX 78249. Abstract Carbon storage regulator A of Borrelia burgdorferi (CsrABb) contributes to vertebrate host-specific adaptation by modulating activation of Rrp2-RpoN-RpoS pathway and is critical for infectivity. We hypothesized that the functions of CsrABb were dependent on environmental signals and on select residues. We analyzed the phenotype of csrABbdeletion and site-specific mutants to determine the conserved and pathogen-specific attributes of CsrABb. Phosphate acetyl transferase (Pta) involved in conversion of acetyl phosphate to acetyl-CoA and post-transcriptionally regulated by CsrABb was reduced or similar in the csrABb mutant compared to control strains under unfed- or fed-tick conditions, respectively. Increased levels of supplemental acetate restored vertebrate host-responsive determinants in csrABb mutant to parental levels indicating that both levels CsrABb and acetyl phosphate/acetyl-CoA balance contribute to the activation of Rrp2-RpoN-RpoS pathway. Site-specific replacement of 8 key residues of CsrABb (8S) with alanines resulted in increased levels of CsrABb, reduced levels of Pta and acetyl-CoA while levels of RpoS, BosR, and other members of rpoS regulon were elevated. Truncation of 7 amino acids at the C-terminus of CsrABb (7D) resulted in reduced csrABb transcripts and post-transcriptionally reduced levels of FliW located upstream of CsrABb. Electrophoretic mobility shift assays revealed increased binding of 8S mutant protein to the CsrA binding box upstream of pta compared to the parental and 7D truncated protein. Two CsrABb binding sites were also identified upstream of fliW within the flgK coding sequence. These observations reveal conserved and unique functions of CsrABb that regulate adaptive gene expression in B. burgdorferi.
Posted on: Thu, 13 Jun 2013 06:14:32 +0000
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