Chemotaxis signaling pathway. Receptors in the plasma membrane initiate a signaling pathway leading to the phosphorylation of the CheY protein. Phosphorylated CheY binds to the flagellar motor and favors clockwise rotation. When an attractant binds to the receptor, this pathway is blocked, and counterclockwise flagellar rotation and, hence, smooth swimming result. When a repellant binds, the pathway is stimulated, leading to an increased concentration of phosphorylated CheY and, hence, more-