receptorCheW

receptorCheW, commonly referred to simply as CheW, is a coupling protein central to bacterial chemotaxis. It links transmembrane chemoreceptors, known as methyl-accepting chemotaxis proteins (MCPs), to the histidine kinase CheA, enabling signal propagation to influence flagellar rotation. In many bacteria, including Escherichia coli, receptorCheW is encoded by the cheW gene and concentrates at the cytoplasmic face of receptor arrays where it participates in the core signaling complex.

Mechanistically, receptorCheW binds both MCP cytoplasmic domains and the P5 domain of CheA, acting as a bridge that stabilizes the receptor–CheA interaction. This arrangement allows CheA to autophosphorylate in response to receptor activity, and transfers the phosphate to downstream signaling proteins such as CheY and CheB. The resulting changes in flagellar rotation modulate swimming behavior, guiding the cell toward attractants or away from repellents. CheW also influences receptor array cooperativity and sensitivity, contributing to the amplified responses observed in chemotaxis.

Structure and diversity: receptorCheW is a relatively small cytoplasmic protein with surfaces specialized for interactions with both MCPs and CheA-P5. Its activity and array organization can be modulated by the presence of multiple CheW homologs in some species, as well as by post-translational modifications that affect signaling. Structural studies have illuminated how CheW supports higher-order arrays that underlie robust and adaptable chemotactic responses.

Biological significance: receptorCheW is essential for efficient chemotaxis in many bacteria. By coordinating receptor input with CheA activity, it enables rapid, graded responses to chemical gradients and contributes to survival in fluctuating environments.