title: A post-translational, c-di-GMP-dependent mechanism regulating flagellar motility.
abstract: Elevated levels of the second messenger cyclic dimeric GMP, c-di-GMP, promote transition of bacteria from single motile cells to surface-attached multicellular communities. Here we describe a post-translational mechanism by which c-di-GMP initiates this transition in enteric bacteria. High levels of c-di-GMP induce the counterclockwise bias in Escherichia coli flagellar rotation, which results in smooth swimming. Based on co-immunoprecipitation, two-hybrid and mutational analyses, the E. coli c-di-GMP receptor YcgR binds to the FliG subunit of the flagellum switch complex, and the YcgR-FliG interaction is strengthened by c-di-GMP. The central fragment of FliG binds to YcgR as well as to FliM, suggesting that YcgR-c-di-GMP biases flagellum rotation by altering FliG-FliM interactions. The c-di-GMP-induced smooth swimming promotes trapping of motile bacteria in semi-solid media and attachment of liquid-grown bacteria to solid surfaces, whereas c-di-GMP-dependent mechanisms not involving YcgR further facilitate surface attachment. The YcgR-FliG interaction is conserved in the enteric bacteria, and the N-terminal YcgR/PilZN domain of YcgR is required for this interaction. YcgR joins a growing list of proteins that regulate motility via the FliG subunit of the flagellum switch complex, which suggests that FliG is a common regulatory entryway that operates in parallel with the chemotaxis that utilizes the FliM-entryway.
authors.affiliation: Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Fang
authors.forename: Mark
authors.initials: M
authors.lastname: Gomelsky
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology*; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005407:Flagella / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D020798:Two-Hybrid System Techniques
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C075660:Flig protein, Bacteria; D011993:Recombinant Fusion Proteins; C415947:YcgR protein, E coli; C062025:bis(3',5')-cyclic diguanylic acid; D006152:Cyclic GMP