Helical Distribution of the Bacterial Chemoreceptor via Colocalization With the Sec Protein Translocation Machinery

Mol Microbiol. 2006 May;60(4):894-906. doi: 10.1111/j.1365-2958.2006.05145.x.

Abstract

In Escherichia coli, chemoreceptor clustering at a cell pole seems critical for signal amplification and adaptation. However, little is known about the mechanism of localization itself. Here we examined whether the aspartate chemoreceptor (Tar) is inserted directly into the polar membrane by using its fusion to green fluorescent protein (GFP). After induction of Tar-GFP, fluorescent spots first appeared in lateral membrane regions, and later cell poles became predominantly fluorescent. Unexpectedly, Tar-GFP showed a helical arrangement in lateral regions, which was more apparent when a Tar-GFP derivative with two cysteine residues in the periplasmic domain was cross-linked to form higher oligomers. Moreover, similar distribution was observed even when the cytoplasmic domain of the double cysteine Tar-GFP mutant was replaced by that of the kinase EnvZ, which does not localize to a pole. Observation of GFP-SecE and a translocation-defective MalE-GFP mutant, as well as indirect immunofluorescence microscopy on SecG, suggested that the general protein translocation machinery (Sec) itself is arranged into a helical array, with which Tar is transiently associated. The Sec coil appeared distinct from the MreB coil, an actin-like cytoskeleton. These findings will shed new light on the mechanisms underlying spatial organization of membrane proteins in E. coli.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Outer Membrane Proteins / analysis
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins
  • Cell Membrane / chemistry
  • Cell Membrane / metabolism*
  • Cell Polarity
  • Chemoreceptor Cells / metabolism*
  • Cytoplasm / chemistry
  • Cytoplasm / metabolism
  • Escherichia coli / chemistry
  • Escherichia coli / metabolism*
  • Escherichia coli / ultrastructure
  • Escherichia coli Proteins / analysis
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Green Fluorescent Proteins / analysis
  • Green Fluorescent Proteins / genetics
  • Membrane Proteins / analysis
  • Membrane Proteins / metabolism
  • Multienzyme Complexes / analysis
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism
  • Mutation
  • Periplasmic Binding Proteins / analysis
  • Periplasmic Binding Proteins / metabolism
  • Protein Transport
  • Receptors, Cell Surface / analysis
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism*
  • SEC Translocation Channels

Substances

  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Escherichia coli Proteins
  • MalE protein, E coli
  • Membrane Proteins
  • Multienzyme Complexes
  • Periplasmic Binding Proteins
  • Receptors, Cell Surface
  • SEC Translocation Channels
  • SecE protein, E coli
  • SecG protein, E coli
  • Tar protein, E coli
  • Green Fluorescent Proteins
  • envZ protein, E coli