The asiA gene of bacteriophage T4 codes for the anti- sigma super(70) protein

The anti- sigma super(70) factor of bacteriophage T4 is a 10-kDa (10K) protein which inhibits the sigma super(70)-directed initiation of transcription by Escherichia coli RNA polymerase holoenzyme. We have partially purified the anti- sigma super(70) factor and obtained the sequence of a C-terminal...

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Bibliographic Details
Published in:Journal of bacteriology 1993-01, Vol.175 (1), p.85-93
Main Authors: Orsini, G, Ouhammouch, M, Le Caer, J-P, Brody, EN
Format: Article
Language:English
Subjects:
Escherichia coli
phage T4
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Summary:The anti- sigma super(70) factor of bacteriophage T4 is a 10-kDa (10K) protein which inhibits the sigma super(70)-directed initiation of transcription by Escherichia coli RNA polymerase holoenzyme. We have partially purified the anti- sigma super(70) factor and obtained the sequence of a C-terminal peptide of this protein. Using reverse genetics, we have identified, at the end of the lysis gene t and downstream of an as yet unassigned phage T4 early promoter, an open reading frame encoding a 90-amino-acid protein with a predicted molecular weight of 10,590. This protein has been overproduced in a phage T7 expression system and partially purified. It shows a strong inhibitory activity towards sigma super(70)-directed transcription RNA polymerase holoenzyme), whereas it has no significant effect on sigma super(70)-independent transcription (by RNA polymerase core enzyme). Our results corroborate the initial observations on the properties of the phage T4 10K anti- sigma super(70) factor, and we therefore propose that the gene which we call asiA, identified in the present study, corresponds to the gene encoding this T4 transcriptional inhibitor.
ISSN:0021-9193