7UBK

Transcription antitermination factor Qlambda, type-II crystal

Summary for 7UBK

• Entry DOI: 10.2210/pdb7ubk/pdb
• Descriptor: Antitermination protein Q, ZINC ION, GLYCEROL, ... (7 entities in total)
• Functional Keywords: rna polymerase, dna binding, transcription, q-dependent antitermination, q antitermination factor, gene regulation
• Biological source: Escherichia phage Lambda
• Total number of polymer chains: 2
• Total formula weight: 33031.81

Authors

Yin, Z.,Ebright, R.H. (deposition date: 2022-03-15, release date: 2022-09-28, Last modification date: 2023-10-18)

Primary citation

Yin, Z.,Bird, J.G.,Kaelber, J.T.,Nickels, B.E.,Ebright, R.H.
In transcription antitermination by Q lambda , NusA induces refolding of Q lambda to form a nozzle that extends the RNA polymerase RNA-exit channel.
Proc.Natl.Acad.Sci.USA, 119:e2205278119-e2205278119, 2022

PubMed Abstract: Lambdoid bacteriophage Q proteins are transcription antipausing and antitermination factors that enable RNA polymerase (RNAP) to read through pause and termination sites. Q proteins load onto RNAP engaged in promoter-proximal pausing at a Q binding element (QBE) and adjacent sigma-dependent pause element to yield a Q-loading complex, and they translocate with RNAP as a pausing-deficient, termination-deficient Q-loaded complex. In previous work, we showed that the Q protein of bacteriophage 21 (Q21) functions by forming a nozzle that narrows and extends the RNAP RNA-exit channel, preventing formation of pause and termination RNA hairpins. Here, we report atomic structures of four states on the pathway of antitermination by the Q protein of bacteriophage λ (Qλ), a Q protein that shows no sequence similarity to Q21 and that, unlike Q21, requires the transcription elongation factor NusA for efficient antipausing and antitermination. We report structures of Qλ, the Qλ-QBE complex, the NusA-free pre-engaged Qλ-loading complex, and the NusA-containing engaged Qλ-loading complex. The results show that Qλ, like Q21, forms a nozzle that narrows and extends the RNAP RNA-exit channel, preventing formation of RNA hairpins. However, the results show that Qλ has no three-dimensional structural similarity to Q21, employs a different mechanism of QBE recognition than Q21, and employs a more complex process for loading onto RNAP than Q21, involving recruitment of Qλ to form a pre-engaged loading complex, followed by NusA-facilitated refolding of Qλ to form an engaged loading complex. The results establish that Qλ and Q21 are not structural homologs and are solely functional analogs.

PubMed: 35951650
DOI: 10.1073/pnas.2205278119

Experimental method

X-RAY DIFFRACTION (1.97 Å)