NMR structure of activated CheY

The CheY protein is the response regulator in bacterial chemotaxis. Phosphorylation of a conserved aspartyl residue induces structural changes that convert the protein from an inactive to an active state. The short half-life of the aspartyl-phosphate has precluded detailed structural analysis of the active protein. Persistent activation of Escherichia coli CheY was achieved by complexation with beryllofluoride (BeF 3 −) and the structure determined by NMR spectroscopy to a backbone r.m.s.d. of 0.58(±0.08) Å. Formation of a hydrogen bond between the Thr87 OH group and an active site acceptor, presumably Asp57·BeF 3 −, stabilizes a coupled rearrangement of highly conserved residues, Thr87 and Tyr106, along with displacement of β4 and H4, to yield the active state. The coupled rearrangement may be a more general mechanism for activation of receiver domains.