Evidence for a compact σ70 conformation in vitro and in vivo

Khalil Joron, Joanna Zamel, Nir Kalisman, Eitan Lerner*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The initiation of transcription in Escherichia coli (E. coli) is facilitated by promoter specificity factors, also known as σ factors, which may bind a promoter only as part of a complex with RNA polymerase (RNAP). By performing in vitro cross-linking mass spectrometry (CL-MS) of apo-σ70, we reveal structural features suggesting a compact conformation compared to the known RNAP-bound extended conformation. Then, we validate the existence of the compact conformation using in vivo CL-MS by identifying cross-links similar to those found in vitro, which deviate from the extended conformation only during the stationary phase of bacterial growth. Conclusively, we provide information in support of a compact conformation of apo-σ70 that exists in live cells, which might represent a transcriptionally inactive form that can be activated upon binding to RNAP.

Original languageEnglish
Article number110140
Issue number6
StatePublished - 21 Jun 2024

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  • Molecular biology


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