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Structure of Mycobacterium smegmatis RNA polymerase Sigma-A holoenzyme
Structural highlights
Function[RPOZ_MYCS2] 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][1] [RPOA_MYCS2] DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates.[HAMAP-Rule:MF_00059][2] [RPOC_MYCS2] DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates.[HAMAP-Rule:MF_01322][3] [RPOB_MYCS2] DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates. This subunit often mutates to generate rifampicin (Rif) resistance. Interaction with RbpA partially restores Rif-inhibited transcription; once the subunit is Rif-resistant however RbpA no longer stimulates transcription.[HAMAP-Rule:MF_01321][4] [A0QW02_MYCS2] Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. This sigma factor is the primary sigma factor during exponential growth.[SAAS:SAAS00535554] Publication Abstract from PubMedBacterial RNA polymerase (RNAP) is essential for gene expression and as such is a valid drug target. Hence, it is imperative to know its structure and dynamics. Here, we present two so far unreported forms of Mycobacteium smegmatis RNAP: core, and holoenzyme containing sigma(A) but no other factors. Each form was detected by cryo-EM in two major conformations. Comparisons of these structures with known structures of other RNAPs reveal a high degree of conformational flexibility of the mycobacterial enzyme, and confirm that region 1.1 of sigma(A) is directed into the primary channel of RNAP. Taken together, the presented study illuminates the conformational changes of unrestrained mycobacterial RNAP.IMPORTANCE We describe here 3D structures of core and holoenzyme forms of mycobacterial RNA polymerase (RNAP) solved by cryo-EM. These structures fill the so far empty spots in the gallery of the pivotal forms of mycobacterial RNAP and illuminate the extent of conformational dynamics of this enzyme. The presented findings may facilitate future designs of antimycobacterial drugs targeting RNAP. The Core and Holoenzyme forms of RNA Polymerase from Mycobacterium smegmatis.,Kouba T, Pospisil J, Hnilicova J, Sanderova H, Barvik I, Krasny L J Bacteriol. 2018 Nov 26. pii: JB.00583-18. doi: 10.1128/JB.00583-18. PMID:30478083[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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