[3] These methyl-accepting chemotaxis receptors are one of the first components in the sensory excitation and adaptation responses in bacteria, which act to alter swimming behaviour upon detection of specific chemicals.

In this manner, a bacterium may swim towards nutrients and away from toxins[4] There are many different types of bacterial 60 kDa transmembrane receptors, which share similar topology and signalling mechanisms.

The structure of the ligand-binding domain comprises a closed or partly opened, four-helical bundle with a left-handed twist.

MCPs undergo two covalent modifications: deamidation and reversible methylation at a number of glutamate residues.

Binding a ligand causes a conformational change in the MCP receptor which translates down the hairpin structure and inhibits its sensor kinase.

This change in direction allows for alternation between smooth swimming and tumbling which biases the bacterial random walk towards attractant.