Resonance assignments of N-terminal receiver domain of sigma factor S regulator RssB from Escherichia coli.

Sigma factor S (σS) are master regulator responsible for the survival of bacteria under extreme conditions. Bacteria start specific gene expression via σS promoter recognition, activating various responses to cope with external conditions. Although this self-protection mechanism is vital for bacteria to propagate and evolve, there are many puzzling research questions to be answered. For example, while interactions between σS, transcription regulator RssB, and anti-adaptor Ira proteins are believed to be responsible for controlling the cellular level of σS, their competition mechanism among them remains elusive. Furthermore, there are still debates on the location of the interface of Ira proteins and RssB and whether phosphorylation on the receiver domain is essential for σS activation remains elusive. While there is one crystal structure for the Escherichia coli receiver domain deposited in the database, the missing regions in the structure become an obstacle for functional and interactive studies. Despite attempts, there is no structure for any protein complex in this important biological process, making it one overlooked area in bacterial transcription. Here, using solution-state NMR, our near-complete resonance assignment for the receiver domain of E. coli RssB provides a basis for future structure determination and interaction studies with its many known and putative ligands.