MICB 325 Study Guide - Quiz Guide: Sigma Factor, Ethyl Methanesulfonate, Mhc Class I Polypeptide-Related Sequence B

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11 Mar 2014
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R e v i e w s: review of the bacterial rna polymerase (rnap). The rnap of bacteria is quite similar from species to species, consisting of four protein major components, alpha, beta, beta-prime, and sigma. For example, the beta subunit of the gram-negative e. coli is about 50% identical in amino acid sequence to the gram-positive b. subtilis. The (sigma) subunit is responsible for recognition of the promoter -10 and -35 sequences. E. coli has seven sigma factors, streptomyces species have around 66. Different sigma factors are induced or repressed in response to different environmental signals, and sets of genes may have a particular promoter sequence that is recognized by one sigma factor but not another. Sigma factors in e. coli are designated by a superscript number that refers to the molecular weight in kilodaltons: 70 (rpod) - the housekeeping Ctd a b sigma factor or also called the primary sigma factor, transcribes most genes in growing cells.