title: Principal sigma subunit of the Caulobacter crescentus RNA polymerase.
abstract: We have identified the gene encoding the Caulobacter crescentus principal sigma subunit, RpoD. The rpoD gene codes for a polypeptide of 653 amino acids with a predicted molecular mass of 72,623 Da (sigma 73). The C. crescentus sigma subunit has extensive amino acid sequence homology with the principal sigma factors of a number of divergent procaryotes. In particular, the segments designated region 2 that are involved in core polymerase binding and promoter recognition were identical among these bacteria despite the fact that the -10 region recognized by the C. crescentus sigma 73 differs significantly from that of the other bacteria. Thus, it appears that additional sigma factor regions must be involved in -10 region recognition. This conclusion was strengthened by a heterologous complementation assay in which C. crescentus sigma 73 was capable of complementing the Escherichia coli rpoD285 temperature-sensitive mutant. Furthermore, C. crescentus sigma 73 conferred new specificity on the E. coli RNA polymerase, allowing the expression of C. crescentus promoters in E. coli. Thus, the C. crescentus sigma 73 appears to have a broader specificity than does the sigma 70 of the enteric bacteria.
authors.affiliation: Department of Biological Sciences, University of South Carolina, Columbia 29208, USA.
authors.forename: J
authors.initials: J
authors.lastname: Malakooti
authors.forename: B
authors.initials: B
authors.lastname: Ely
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D016935:Caulobacter crescentus / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D002453:Cell Cycle; D003001:Cloning, Molecular; D012321:DNA-Directed RNA Polymerases / Q000096:biosynthesis / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000096:biosynthesis / Q000235:genetics*; D013045:Species Specificity; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D012333:RNA, Messenger; D012808:Sigma Factor; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases