7dy6
A refined cryo-EM structure of an Escherichia coli RNAP-promoter open complex (RPo) with SspA
Structural highlights
FunctionSSPA_ECOLI Forms an equimolar complex with the RNA polymerase holoenzyme (RNAP) but not with the core enzyme. It is synthesized predominantly when cells are exposed to amino acid starvation, at which time it accounts for over 50% of the total protein synthesized. It is involved in the transition from P1 early to P1 late gene expression. Rnk and SspA can functionally replace P.aeruginosa alginate regulatory gene algR2. Publication Abstract from PubMedStringent starvation protein A (SspA) involved in nucleotide metabolism, acid tolerance and virulence of bacteria has been demonstrated to function as a transcription factor to regulate sigma(70)-dependent gene transcription through interacting with sigma(70) region 4 and the zinc binding domain (ZBD) of E. coli RNA polymerase (EcoRNAP) beta' subunit simultaneously. Despite extensive biochemical and structural analyses were reported recently, the interactions of SspA with RNAP are not comprehensively understood. Here, we reprocessed our previous cryo-EM dataset of EcoRNAP-promoter open complex with SspA (SspA-RPo) and obtained a significantly improved density map. Unexpectedly, the new map showed that SspA interacts with both N-terminal helix of beta' subunit (beta'NuTauEta) and omega subunit, which contributes to stabilize the SspA-EcoRNAP sigma(70) holoenzyme complex. Sequence alignments and phylogenetic tree analyses of N-terminal sequences of beta' subunit from different classes of bacteria revealed that beta'NuTauEta is highly conserved and exclusively found in low-GC-content Gram-negative bacteria that harbor SspA, implying a co-evolution of beta'NuTauEta and SspA. The transcription assays of wild-type SspA and its mutants demonstrated the interaction between SspA and beta'NuTauEta facilitates the transcription regulation of SspA. Together, our results provide a more comprehensive insight into the interactions between SspA and RNAP and their roles in bacterial transcription regulation. A unique binding between SspA and RNAP beta(')NTH across low-GC Gram-negative bacteria facilitates SspA-mediated transcription regulation.,Wang F, Feng Y, Shang Z, Lin W Biochem Biophys Res Commun. 2021 Oct 27;583:86-92. doi: , 10.1016/j.bbrc.2021.10.048. PMID:34735884[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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