Functional Analysis of theHelicobacter pyloriFlagellar Switch Proteins

Abstract

Helicobacter pylori uses flagellum-mediated chemotaxis to promote infection. Bacterial flagella change rotational direction by changing the state of the flagellar motor via a subcomplex referred to as the switch. Intriguingly, the H. pylori genome encodes four switch complex proteins, FliM, FliN, FliY, and FliG, instead of the more typical three of Escherichia coli or Bacillus subtilis. Our goal was to examine whether and how all four switch proteins participate in flagellation. Previous work determined that FliG was required for flagellation, and we extend those findings to show that all four switch proteins are necessary for normal numbers of flagellated cells. Furthermore, while fliY and fliN are partially redundant with each other, both are needed for wild-type levels of flagellation. We also report the isolation of an H. pylori strain containing an R54C substitution in fliM, resulting in bacteria that swim constantly and do not change direction. Along with data demonstrating that CheY-phosphate interacts with FliM, these findings suggest that FliM functions in H. pylori much as it does in other organisms.

Shewanella oneidensis MR-1 nanowires are outer membrane and periplasmic extensions of the extracellular electron transport components

“…The amphiphilic nature of this molecule hinders it from freely crossing the membrane into the cellular interior except through the endocytic pathway, as extensively characterized in eukaryotic cells (30,31). FM 4-64 has also been widely used in bacterial cells and shown to specifically label membranes but not extracellular protein filaments such as flagella (32,33), except in a few bacterial species where flagella are coated in membrane sheaths (34). To our surprise, the entire length of the Shewanella nanowires was clearly stained with this reliable lipid bilayer dye (Fig.…”

Imaging the Motility and Chemotaxis Machineries in Helicobacter pylori by Cryo-Electron Tomography

“…The H. pylori genome encodes four flagellar switch proteins (FliG, FliM, FliN, and FliY) (15) compared to the three switch proteins (FliG, FliM, and FliN) in Salmonella and E. coli. It has been shown that each of the four switch proteins is required for wild-type levels of flagellation and function.…”

Structural Characterization at the Atomic Level of a Molecular Nano-Machine: The State of the Art of <i>Helicobacter Pylori</i> Flagellum Organization

“…Chen et al (2011) demonstrated by some cryo-EM studies that the main core of C-ring in most of the bacteria is principally regulated by the presence of FliG, FliM and FliN, but not FliY. According to Lowenthal et al (2009), FliY protein has an N-termianl domain that belongs to CheC/CheX/FliY/FliM family. Due to its feature, it is possible that FliY may substitute FliM in FliG Cdomain interaction, but experimental confirmation is lacking.…”

“…Moreover, FliN is involved in the direct binding of the regulator protein CheY-P (Paul and Blair, 2006). Lowenthal et al (2009) performed some alignment of FliN and FliY sequences taken from well characterized bacteria. They noticed highly conserved structural regions, even though some specific amino acids were not.…”