Transcription factor Escherichia coli

Schwartz CJ, Giel JL, Patschkowski T, et al. 2001. IscR, an Fe-S cluster-containing transcription factor, represses expression of Escherichia coli genes encoding Fe-S cluster assembly proteins. Proc Natl Acad Sci USA 98 14895-900. 

Escherichia coli genes are transcribed once per second, others less than once per cell generation. Much of this variation is due to differences in promoter sequence. In the absence of regulatory proteins, differences in promoter sequences may affect the frequency of transcription initiation by a factor of 1,000 or more. Most E. coli promoters have a sequence close to a consensus (Fig. 28-2). Mutations that result in a shift away from the consensus sequence usually decrease promoter function conversely, mutations toward consensus usually enhance promoter function. 

Alternative Sigma Factors Trigger Initiation of Transcription at Different Promoters Elongation of the Transcript Termination of Transcription Comparison of Escherichia coli RNA Polymerase with DNA Poll and PolIII... 

Relatively recently Fe/S proteins have been found to function in the regulation of biosynthesis. This can be by promoting deoxyribonucleic acid (DNA) transcription, e.g. the [2Fe-2S] containing Escherichia coli superoxide-activated (SoxR) transcription activator [10-12], or the presumably [4Fe-4S]-containing E. coli transcription factor fumarate nitrate reduction (FNR) [13,14], Alternatively, the Fe/S protein can act by interference with messenger ribonucleic acid (mRNA) translation, i.e., the iron regulatory proteins (IRPs) [15,16], These interactions are stoichiometric, therefore not catalytic. Presumably, they are also a form of sensoring, namely, of oxidants and/or iron [17],... 

Bicyclomycin is certainly the most important compound to be cited in this section. Because of its broad spectrum of activity displayed against Gram-negative bacteria (such as Escherichia coli, Klebsiella, Salmonella, Shigella, and Citrobacter), coupled with its low toxicity, bicyclomycin was introduced into the market under the trade name Bicozamycin. The mode of action of bicyclomycin was studied in the 1980s and early 1990s, and only information concerning its locus of action in E. coli, that is, the rho transcription termination factor (rho is a protein responsible for termination of RNA... 

B.L. Stitt. 2001. Escherichia coli transcription termination factor Rho hinds and hydrolyzes ATP using a single class of three sites Bio-chemistry 40 2276-2281. (PubMed)... 

Although the mechanism whereby proteins are synthesized is the same in all living forms, classical distinctions exist between eucaryal (post-transcriptional) and bacterial (co-transcriptional) translation. In-frame read-out of (usually polycistronic) bacterial mRNAs is established via Shine-Dalgarno mRNA 16S-rRNA recognition mechanisms polypeptide synthesis is initiated by a formylated methionine and the initiation reactions are assisted by a limited number of protein factors (three in Escherichia coli) that primarily influence kinetic parameters [3],... 

DeShazer D, Wood GE, Friedman RL (1995) Identification of a Bordetella pertussis regulatory factor required for transcription of the pertussis toxin operon in Escherichia coli. In J. Bacterial. 177 3801 -3807. 

Another approach to inexpensive labelling of proteins is by means of cell-free protein synthesis.48 50 These in vitro expression systems use a crude Escherichia coli fraction as a source of ribosomes and other factors necessary for the synthesis of proteins, T7 RNA polymerase for transcription, and dialysis to maintain levels of amino acids and nucleotides. In principle, the technology is capable of labelling proteins at specific sites without isotope scrambling and also of producing labelled proteins from small volumes of labelled medium. 

Mossbauer studies of the FNR transcription factor in whole Escherichia coli cells... 

Tomura D, Obika K, Fukamizu A, Shoun H (1994) Nitric-oxide reductase cytochrome-P-450 gene, CYP 55, of the fungus Fusarium-oxysporum containing a potential binding-site for FNR, the transcription factor involved in the regulation of anaerobic growth of Escherichia coli. J Biochem 116 88-94... 

We have mentioned how DNA polymerase I from Escherichia coli extends the DNA chain, but how does it initiate the chain A clue to the mechanism was obtained when it was observed that rifampicin, an inhibitor of RNA polymerase, also inhibits the conversion of a phage single stranded into a double stranded DNA circle. This suggested that DNA synthesis is initiated by RNA priming. It is now established that the initiation of DNA synthesis by DNA polymerase I requires RNA and DNA polymerase, ribose and deoxyribose triphosphates, an unwinding protein and other factors whose roles are still unclear. The initiation step seems to involve a transcriptional operation by RNA polymerase. The newly synthesized RNA serves as primer for DNA polymerase I, yielding an RNA-DNA complex and the primary RNA is excised by a nuclease [236, 237]. 

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