Suppressor Analysis of the MotB(D33E) Mutation To Probe Bacterial Flagellar Motor Dynamics Coupled with Proton Translocation

摘要: MotA and MotB form the stator of proton-driven bacterial flagellar motor, which conducts protons couples proton flow with motor rotation. Asp-33 Salmonella enterica serovar Typhimurium MotB, is a putative proton-binding site, critical for torque generation. However, mechanism energy coupling remains unknown. Here, we carried out genetic motility analysis slowly motile motB(D33E) mutant its pseudorevertants. We first confirmed that poor due to neither protein instability, mislocalization, nor impaired interaction MotA. isolated 17 pseudorevertants identified suppressor mutations in transmembrane helices TM2 TM3 TM periplasmic domain MotB. The stall produced by was about half wild-type level, while those were recovered nearly levels. high-speed rotations motors under low-load conditions still significantly impaired, suggesting rate translocation severely limited at high speed. These results suggest second-site recover generation step involving stator-rotor interactions coupled protonation/deprotonation Glu-33 but not maximum conductivity.