FIG. 2.

Discovery of a CheY residue specifically needed for CheZ-mediated dephosphorylation. Green diamond, CheY; red square, CheZ. (A) Summary of CheY dephosphorylation reactions. CheY autophosphorylates at aspartate-57. The other active-site residues needed for that reaction are also involved in autodephosphorylation. CheZ residue Q147 plays an active role in accelerating the dephosphorylation of CheY. The CheY-N59R mutation has no effect on autodephosphorylation but disrupts CheZ-mediated dephosphorylation, even though N59 itself has no role in the CheZ-mediated reaction. (B) Mechanism of the CheY-N59R effect deduced by Silversmith et al. (15). The arginine side chain makes a salt bridge to the carboxyl group of CheY-E89, which prevents it from participating, as it normally does, in the CheZ-mediated reaction.