The antiactivator FleN uses an allosteric mechanism to regulate σ<sup>54</sup>-dependent expression of flagellar genes in <i>Pseudomonas aeruginosa</i>.
basic_science · Level V
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- Record sourced from PubMed, PMID 34669473.
- Also identified by DOI 10.1126/sciadv.abj1792 and PMC identifier 8528422.
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Abstract
Diverse sigma factors associate with the RNA polymerase (RNAP) core enzyme to initiate transcription of specific target genes in bacteria. σ<sup>54</sup>-Mediated transcription uses AAA+ activators that utilize their ATPase activity for transcription initiation. FleQ is a σ<sup>54</sup>-dependent master transcriptional regulator of flagellar genes in <i>Pseudomonas aeruginosa</i>. The ATPase activity of FleQ is regulated via a P-loop ATPase, FleN, through protein-protein interaction. We report a high-resolution crystal structure of the AAA+ domain of FleQ in complex with antiactivator FleN. The data reveal that FleN allosterically prevents ATP binding to FleQ. Furthermore, FleN remodels the region of FleQ essential for engagement with σ<sup>54</sup> for transcription initiation. Disruption of the conserved protein-protein interface, by mutation, shows motility and transcription defects in vivo and multiflagellate phenotype. Our study provides a detailed mechanism used by monoflagellate bacteria to fine-tune the expression of flagellar genes to form and maintain a single flagellum.