6p1b

Publication Abstract from PubMed

Lambdoid bacteriophage Q protein mediates the switch from middle to late bacteriophage gene expression by enabling RNA polymerase (RNAP) to read through transcription terminators preceding bacteriophage late genes. Q loads onto RNAP engaged in promoter-proximal pausing at a Q binding element (QBE) and adjacent sigma-dependent pause element (SDPE) to yield a Q-loading complex, and Q subsequently translocates with RNAP as a pausing-deficient, termination-deficient Q-loaded complex. Here, we report high-resolution structures of 4 states on the pathway of antitermination by Q from bacteriophage 21 (Q21): Q21, the Q21-QBE complex, the Q21-loading complex, and the Q21-loaded complex. The results show that Q21 forms a torus, a "nozzle," that narrows and extends the RNAP RNA-exit channel, extruding topologically linked single-stranded RNA and preventing the formation of pause and terminator hairpins.

Structural basis of Q-dependent antitermination.,Yin Z, Kaelber JT, Ebright RH Proc Natl Acad Sci U S A. 2019 Sep 10;116(37):18384-18390. doi:, 10.1073/pnas.1909801116. Epub 2019 Aug 27. PMID:31455742^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.