6k4y
From Proteopedia
CryoEM structure of sigma appropriation complex
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] [RPOC_ECOLI] DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates.[HAMAP-Rule:MF_01322] [MOTA_BPT4] Required for the transcriptional activation of middle promoters. Middle promoters are characterized by the presence of the conserved sequence [AT]3TGCTTNA (MotA box). MotA binds directly to MotA boxes. [RPOB_ECOLI] DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates.[HAMAP-Rule:MF_01321] [RPOA_ECOLI] DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. This subunit plays an important role in subunit assembly since its dimerization is the first step in the sequential assembly of subunits to form the holoenzyme.[HAMAP-Rule:MF_00059] [RPOZ_ECOLI] Promotes RNA polymerase assembly. Latches the N- and C-terminal regions of the beta' subunit thereby facilitating its interaction with the beta and alpha subunits.[HAMAP-Rule:MF_00366] [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. Publication Abstract from PubMedBacteriophage T4 middle promoters are activated through a process called sigma appropriation, which requires the concerted effort of two T4-encoded transcription factors: AsiA and MotA. Despite extensive biochemical and genetic analyses, puzzle remains, in part, because of a lack of precise structural information for sigma appropriation complex. Here, we report a single-particle cryo-electron microscopy (cryo-EM) structure of an intact sigma appropriation complex, comprising AsiA, MotA, Escherichia coli RNA polymerase (RNAP), sigma70 and a T4 middle promoter. As expected, AsiA binds to and remodels sigma region 4 to prevent its contact with host promoters. Unexpectedly, AsiA undergoes a large conformational change, takes over the job of sigma region 4 and provides an anchor point for the upstream double-stranded DNA. Because sigma region 4 is conserved among bacteria, other transcription factors may use the same strategy to alter the landscape of transcription immediately. Together, the structure provides a foundation for understanding sigma appropriation and transcription activation. Structural basis of sigma appropriation.,Shi J, Wen A, Zhao M, You L, Zhang Y, Feng Y Nucleic Acids Res. 2019 Aug 8. pii: 5545004. doi: 10.1093/nar/gkz682. PMID:31392983[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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