Lambda N as a model substrate for studying the mechanism of Escherichia coli ATP-dependent protease Lon as a regulatory enzyme.

As an ATP-dependent protease, the quality control functions of Lon have been extensively studied and reviewed in the literature. By contrast, very little research has been conducted to investigate Lons physiological functions and its mechanism as a regulatory protease. In this manuscript, we provided a survey of literature and data to convey that the lambda N ({lambda}N) protein is a suitable Escherichia coli Lon (ELon) substrate for studying the role played by Lon in regulating an RNA transcription process. For proof of principle, we demonstrated that the minimal component of the RNA transcription complex containing RNA polymerase (RNAP) and the {sigma} factor can inhibit {lambda}N degradation by ELon through SDS-PAGE, and the carboxyl-terminal of {lambda}N is important for Lon competing with RNAP interaction. Using negative stain electron microscopy, we obtained structural evidence to show that {lambda}N lacking the carboxyl-terminal flanked by residues 99-107 interacted with ELon differently than full-length {lambda}N. Taken together, the activity and EM data provide a starting point for performing a physiological enzymology study on the contribution of ELon toward RNA transcription.