mCpT

McpT, or methyl-accepting chemotaxis protein T, is a bacterial chemoreceptor that functions as a transmembrane sensor in certain Gram-negative bacteria. It belongs to the larger family of methyl-accepting chemotaxis proteins (MCPs), which detect chemical cues and regulate movement by influencing the activity of the CheA kinase within the chemotaxis signaling pathway. McpT has been described in Pseudomonas putida and closely related species, where it contributes to chemotaxis toward environmental aromatic compounds, though the exact ligand range can vary by strain.

Like other MCPs, McpT is expected to adopt a modular architecture that includes two transmembrane helices, a periplasmic ligand-binding domain, and a substantial cytoplasmic signaling region. The cytoplasmic portion typically contains a HAMP domain and extended coiled-coil regions that facilitate interaction with the CheA-CheW signaling complex. In the cell, McpT forms dimers and can assemble into higher-order arrays at the cell pole, enabling efficient signal transmission to the downstream chemotaxis machinery.

Functionally, McpT participates in chemotactic responses by modulating CheA autophosphorylation through interactions with CheW and other signaling components. Ligand binding or unbinding to the periplasmic domain leads to conformational changes transmitted via the transmembrane segments to alter the motor bias of the flagella, guiding the bacterium toward favorable conditions or away from repellents.

Evolutionarily, McpT is part of a diverse MCP family with receptors that vary in number and ligand specificity across species and ecological niches. As with other MCPs, its signaling output is influenced by methylation state and adaptation enzymes such as CheR and CheB.