Structural basis of ECF-σ-factor-dependent transcription initiation.

ABSTRACT: Extracytoplasmic (ECF) σ factors, the largest class of alternative σ factors, are related to primary σ factors, but have simpler structures, comprising only two of six conserved functional modules in primary σ factors: region 2 (σR2) and region 4 (σR4). Here, we report crystal structures of transcription initiation complexes containing Mycobacterium tuberculosis RNA polymerase (RNAP), M. tuberculosis ECF σ factor σ^L, and promoter DNA. The structures show that σR2 and σR4 of the ECF σ factor occupy the same sites on RNAP as in primary σ factors, show that the connector between σR2 and σR4 of the ECF σ factor-although shorter and unrelated in sequence-follows the same path through RNAP as in primary σ factors, and show that the ECF σ factor uses the same strategy to bind and unwin

SUBMITTER: Lin W 

PROVIDER: S-EPMC6372665 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature