5tw1
From Proteopedia
Crystal structure of a Mycobacterium smegmatis transcription initiation complex with RbpA
Structural highlights
Function[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] [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][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] [RBPA_MYCS2] Binds to RNA polymerase (RNAP), probably stimulating transcriptions from principal, but not alternative sigma factor promoters (By similarity). Partially restores transcription in the presence of rifampicin (Rif) in vitro; overexpression leads to an increase in the Rif tolerance in vivo, with smaller colonies. Seems to act by removing Rif from its binding site and preventing its further binding. No longer stimulates transcription in Rif-resistant RNA polymerase (with mutations in rpoB).[3] [4] [RPOC_MYCS2] DNA-dependent RNA polymerase catalyzes the transcription of DNA into RNA using the four ribonucleoside triphosphates as substrates.[HAMAP-Rule:MF_01322][5] [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][6] Publication Abstract from PubMedRbpA and CarD are essential transcription regulators in mycobacteria. Mechanistic analyses of promoter open complex (RPo) formation establish thatRbpA and CarD cooperatively stimulate formation of anintermediate (RP2) leading to RPo; formation of RP2 islikely a bottleneck step at the majority of mycobacterial promoters. Once RPo forms, CarD also disfavors its isomerization back to RP2.We determined a 2.76 A-resolution crystal structure of a mycobacterial transcription initiation complex (TIC) with RbpA as well as a CarD/RbpA/TIC model. Both CarD and RbpA bind near the upstream edge of the -10 element where they likely facilitate DNA bending and impede transcription bubble collapse. In vivo studies demonstrate the essential role of RbpA, effects of RbpA truncations on transcription and cell physiology, and indicate additional functions for RbpA not evident in vitro. This work provides a framework to understand the control of mycobacterial transcriptionby RbpA and CarD. Structure and function of the mycobacterial transcription initiation complex with the essential regulator RbpA.,Hubin EA, Fay A, Xu C, Bean JM, Saecker RM, Glickman MS, Darst SA, Campbell EA Elife. 2017 Jan 9;6. pii: e22520. doi: 10.7554/eLife.22520. PMID:28067618[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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