1tlh
From Proteopedia
T4 AsiA bound to sigma70 region 4
Structural highlights
Function[ASIA_BPT4] Transcriptional inhibitor. Inhibits sigma 70-directed transcription by weakening its interaction with the core of the host's RNA polymerase. This allows Gp55 to successfully compete for the core enzyme. Plays an important role during the prereplicative period of phage T4 development.[1] [2] [RPOD_ECOLI] Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. This is the primary sigma factor of this bacterium. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBacteriophage T4 AsiA is a versatile transcription factor capable of inhibiting host gene expression as an 'anti-sigma' factor while simultaneously promoting gene-specific expression of T4 middle genes in conjunction with T4 MotA. To accomplish this task, AsiA engages conserved region 4 of Eschericia coli sigma70, blocking recognition of most host promoters by sequestering the DNA-binding surface at the AsiA/sigma70 interface. The three-dimensional structure of an AsiA/region 4 complex reveals that the C-terminal alpha helix of region 4 is unstructured, while four other helices adopt a completely different conformation relative to the canonical structure of unbound region 4. That AsiA induces, rather than merely stabilizes, this rearrangement can be realized by comparison to the homologous structures of region 4 solved in a variety of contexts, including the structure of Thermotoga maritima sigmaA region 4 described herein. AsiA simultaneously occupies the surface of region 4 that ordinarily contacts core RNA polymerase (RNAP), suggesting that an AsiA-bound sigma70 may also undergo conformational changes in the context of the RNAP holoenzyme. T4 AsiA blocks DNA recognition by remodeling sigma70 region 4.,Lambert LJ, Wei Y, Schirf V, Demeler B, Werner MH EMBO J. 2004 Aug 4;23(15):2952-62. Epub 2004 Jul 15. PMID:15257291[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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