title: Mutagenesis of region 4 of sigma 28 from Chlamydia trachomatis defines determinants for protein-protein and protein-DNA interactions.
abstract: Transcription factor sigma(28) in Chlamydia trachomatis (sigma(28)(Ct)) plays a role in the regulation of genes that are important for late-stage morphological differentiation. In vitro mutational and genetic screening in Salmonella enterica serovar Typhimurium was performed in order to identify mutants with mutations in region 4 of sigma(28)(Ct) that were defective in sigma(28)-specific transcription. Specially, the previously undefined but important interactions between sigma(28)(Ct) region 4 and the flap domain of the RNA polymerase beta subunit (beta-flap) or the -35 element of the chlamydial hctB promoter were examined. Our results indicate that amino acid residues E206, Y214, and E222 of sigma(28)(Ct) contribute to an interaction with the beta-flap when sigma(28)(Ct) associates with the core RNA polymerase. These residues function in contacts with the beta-flap similarly to their counterpart residues in Escherichia coli sigma(70). Conversely, residue Q236 of sigma(28)(Ct) directly binds the chlamydial hctB -35 element. The conserved counterpart residue in E. coli sigma(70) has not been reported to interact with the -35 element of the sigma(70) promoter. Observed functional disparity between sigma(28)(Ct) and sigma(70) region 4 is consistent with their divergent properties in promoter recognition. This work provides new insight into understanding the molecular basis of gene regulation controlled by sigma(28)(Ct) in C. trachomatis.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 021181, USA.
authors.forename: Ziyu
authors.initials: Z
authors.lastname: Hua
authors.forename: Xiancai
authors.initials: X
authors.lastname: Rao
authors.forename: Xiaogeng
authors.initials: X
authors.lastname: Feng
authors.forename: Xudong
authors.initials: X
authors.lastname: Luo
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Liang
authors.forename: Li
authors.initials: L
authors.lastname: Shen
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002692:Chlamydia trachomatis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016415:Sequence Alignment; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C064971:FliA protein, Bacteria; D012808:Sigma Factor; D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit