The bacterial flagellar protein export apparatus processively transports flagellar proteins even with extremely infrequent ATP hydrolysis

• Published in: Scientific reports 2014-12, Vol.4 (1), p.7579, Article 7579
• Main Authors: Minamino, Tohru, Morimoto, Yusuke V., Kinoshita, Miki, Aldridge, Phillip D., Namba, Keiichi
• Format: Article
• Language: English
• Subjects: 101/28; 14/34; 631/326/41/2180; 631/57/1464; 631/57/343/2280; 82; 82/29; 82/83; Adenosine triphosphatase; Adenosine Triphosphate - genetics; Adenosine Triphosphate - metabolism; Amino Acid Substitution; ATP; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Deletion mutant; Energy sources; Escherichia coli - genetics; Escherichia coli - metabolism; Flagella; Flagella - genetics; Flagella - metabolism; Humanities and Social Sciences; Hydrolysis; multidisciplinary; Mutation, Missense; Protein transport; Protein Transport - physiology; Proteins; Proton-Translocating ATPases - genetics; Proton-Translocating ATPases - metabolism; Protonmotive force; Salmonella - genetics; Salmonella - metabolism; Science; Self-assembly; Translocation
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep07579

For self-assembly of the bacterial flagellum, a specific protein export apparatus utilizes ATP and proton motive force (PMF) as the energy source to transport component proteins to the distal growing end. The export apparatus consists of a transmembrane PMF-driven export gate and a cytoplasmic ATPase complex composed of FliH, FliI and FliJ. The FliI 6 FliJ complex is structurally similar to the α 3 β 3 γ complex of F O F 1 -ATPase. FliJ allows the gate to efficiently utilize PMF to drive flagellar protein export but it remains unknown how. Here, we report the role of ATP hydrolysis by the FliI 6 FliJ complex. The export apparatus processively transported flagellar proteins to grow flagella even with extremely infrequent or no ATP hydrolysis by FliI mutation (E211D and E211Q, respectively). This indicates that the rate of ATP hydrolysis is not at all coupled with the export rate. Deletion of FliI residues 401 to 410 resulted in no flagellar formation although this FliI deletion mutant retained 40% of the ATPase activity, suggesting uncoupling between ATP hydrolysis and activation of the gate. We propose that infrequent ATP hydrolysis by the FliI 6 FliJ ring is sufficient for gate activation, allowing processive translocation of export substrates for efficient flagellar assembly.