Methyl-accepting chemotaxis proteins: a core sensing element in prokaryotes and archaea

Abstract

Chemotaxis is the directed motility by means of which microbes sense chemical cues and relocate towards more favorable environments. Methyl-accepting chemotaxis proteins (MCPs) are the most common receptors in bacteria and archaea. They are arranged as trimers of dimers that, in turn, form hexagonal arrays in the cytoplasmic membrane or in the cytoplasm. Several different classes of MCPs have been identified according to their ligand binding region and membrane topology. MCPs have been further classified based on the length and sequence conservation of their cytoplasmic domains. Clusters of membrane-embedded MCPs often localize to the poles of the cell, whereas cytoplasmic MCPs can be targeted to the poles or distributed throughout the cell body. MCPs play an important role in cell survival, pathogenesis, and biodegradation. Bacterial adaptation to diverse environmental conditions promotes diversity among the MCPs. This review summarizes structure, classification, and structure-activity relationship of the known MCP receptors, with a brief overview of the signal transduction mechanisms in bacteria and archaea.

What bacteria want

“…Depending on the nature of the output domains (if present), RRs may serve as transcriptional regulators, control flagellar or twitching motility, or control other signalling systems, for example, by synthesizing or hydrolysing second messengers cAMP or c‐di‐GMP (Galperin, ; ; Gao et al ., ; Gao and Stock, ; Zschiedrich et al ., ). Methyl‐accepting chemotaxis sensor proteins (MCPs) respond to their respective signals by interacting with the chemotaxis‐specific HK CheA, which causes phosphorylation of the stand‐alone REC domain RR CheY. Interaction of CheY~P with the flagellar FliM protein affects the direction of flagellar rotation (Ortega et al ., ; Salah Ud‐Din and Roujeinikova, ; Bi and Sourjik, ). Some MCPs serve as inputs for alternative signal transduction pathways (Hickman et al ., ; Willett and Kirby, ).…”

Thriving in Wetlands: Ecophysiology of the Spiral-Shaped Methanotroph Methylospira mobilis as Revealed by the Complete Genome Sequence

“…MCPs recognize various signals and transmit this information to CheA, which ultimately controls the direction of flagellar motor rotation [71]. Therefore, genes encoding MCPs were mainly found in genomes of motile microbes [72]. Overall, the repertoire of signal transduction proteins in the studied organisms reflects their lifestyles.…”

Decoding the chemotactic signal

“…An MCP receptor core‐signaling unit is composed of a trimer of dimers, and the LBD is commonly located at the periplasmic dimer interface. Ligand binding induces conformational and/or dynamic changes that are transmitted through the plasma membrane to a cytosolic “signal conversion module” known as a HAMP domain, which in turn transmits these changes to the signaling domain (SD), the most conserved domain of MCP receptors . These changes in the SD inhibit autophosphorylation of the histidine kinase CheA through a cytosolic adaptor, CheW.…”

“…The MCP receptor core‐signaling unit complexes with CheA and CheW to form supramolecular hexagonal arrays (chemosensory arrays) consisting of thousands of proteins, and these chemosensory arrays allow for significant amplification (at least 50‐fold) of the chemoeffector stimulus . While the MCP architecture described is the best studied and most common architecture, MCP receptors can adopt alternative architectures, although all contain the conserved SD …”