RESUMEN
Helicobacter pylori requires flagellar motility and orientation to persist actively in its habitat. A particular feature of flagella in most Helicobacter species including H. pylori is a membraneous flagellar sheath. The anti-sigma factor FlgM of H. pylori is unusual, since it lacks an N-terminal domain present in other FlgM homologs, e.g., FlgM of Salmonella spp., whose regulatory function is intimately coupled to its secretion through the flagellar type III secretion system. The aim of the present study was to characterize the localization and secretion of the short H. pylori FlgM in the presence of a flagellar sheath and to elucidate its interaction with other flagellar proteins, such as the basal body protein FlhA, which was previously shown to cooperate with FlgM for regulation. H. pylori FlgM was only released into the medium in minor amounts in wild-type bacteria, where the bulk amount of the protein was retained in the cytoplasm. Some FlgM was detected in the flagellar fraction. FlgM was expressed in flhA mutants and was less soluble and differentially localized in bacterial fractions of the flhA mutant in comparison to wild-type bacteria. FlgM-green fluorescent protein and FlgM-V5 translational fusions were generated and expressed in H. pylori. FlgM displayed a predominantly polar distribution and interacted with the C-terminal domain of FlhA (FlhA(C)). We suggest that, in H. pylori, FlgM secretion may not be paramount for its regulatory function and that protein interactions at the flagellar basal body may determine the turnover and localization of functional FlgM.
Asunto(s)
Proteínas Bacterianas/metabolismo , Citoplasma/metabolismo , Flagelos/metabolismo , Helicobacter pylori/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas Bacterianas/genética , Electroforesis en Gel de Poliacrilamida , Regulación Bacteriana de la Expresión Génica , Prueba de Complementación Genética , Helicobacter pylori/genética , Proteínas de la Membrana/genética , Microscopía Electrónica , Mutación , Reacción en Cadena de la Polimerasa , Unión Proteica , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Técnicas del Sistema de Dos HíbridosRESUMEN
BACKGROUND & AIMS: Little is known about how bacteria establish chronic infections of mucosal surfaces. Helicobacter pylori (H. pylori), a chronic pathogen that lives in the gastric mucosa of humans, interacts with the trefoil factor family (TFF) protein TFF1, which is found in gastric mucus. We aimed to characterize the interaction of H. pylori with TFF1 and to assess the role of this interaction in mediating colonization. METHODS: Subcellular fractions of H. pylori were immobilized and then probed with TFF1, TFF2, or TFF3. The effect of glycosidases and preincubation with monosaccharides on the interaction and binding of TFF1 to a H. pylori adhesin was assessed. The interaction between H. pylori adhesin and TFF1 was characterized using surface plasmon resonance, flow cytometry, nondenaturing polyacrylamide gel electrophoresis, coimmunofluoresence, and incubation with tissue sections. RESULTS: The H. pylori core oligosaccharide portion (rough form) of lipopolysaccharide (RF-LPS) bound to TFF1 and to a lesser extent TFF3; this interaction was inhibited by incubation of RF-LPS with mannosidase, glucosidase, or mixed monosaccharides. TFF1 also bound to human serum albumin-conjugated mannose and glucose. The optimum pH for binding was 5.0-6.0 for TFF1 and 7.0 for TFF3. H. pylori bound TFF1 in gastric mucus ex vivo; binding of LPS-coated latex beads to human antral gastric tissue was inhibited by TFF1. CONCLUSIONS: TFF1 interacts specifically with H. pylori RF-LPS. The pH dependence of this interaction indicates that binding of H. pylori to TFF1 in the stomach could promote colonization of the mucus layer adjacent to the gastric epithelial surface.