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Articles by Kaifeng Hu
Total Records ( 1 ) for Kaifeng Hu
  Jun Hu , Kaifeng Hu , David C. Williams, Jr. , Michal E. Komlosh , Mengli Cai and G. Marius Clore
  Solution structures of complexes between the isolated A (IIAMan) and B (IIBMan) domains of the cytoplasmic component of the mannose transporter of Escherichia coli have been solved by NMR. The complex of wild-type IIAMan and IIBMan is a mixture of two species comprising a productive, phosphoryl transfer competent complex and a non-productive complex with the two active site histidines, His-10 of IIAMan and His-175 of IIBMan, separated by ∼25Å. Mutation of the active site histidine, His-10, of IIAMan to a glutamate, to mimic phosphorylation, results in the formation of a single productive complex. The apparent equilibrium dissociation constants for the binding of both wild-type and H10E IIAMan to IIBMan are approximately the same (KD ∼ 0.5 mM). The productive complex can readily accommodate a transition state involving a pentacoordinate phosphoryl group with trigonal bipyramidal geometry bonded to the Nε2 atom of His-10 of IIAMan and the Nδ1 atom of His-175 of IIBMan with negligible (<0.2Å) local backbone conformational changes in the immediate vicinity of the active site. The non-productive complex is related to the productive one by a ∼90° rotation and ∼37Å translation of IIBMan relative to IIAMan, leaving the active site His-175 of IIBMan fully exposed to solvent in the non-productive complex. The interaction surface on IIAMan for the non-productive complex comprises a subset of residues used in the productive complex and in both cases involves both subunits of IIAMan. The selection of the productive complex by IIAMan(H10E) can be attributed to neutralization of the positively charged Arg-172 of IIBMan at the center of the interface. The non-productive IIAMan-IIBMan complex may possibly be relevant to subsequent phosphoryl transfer from His-175 of IIBMan to the incoming sugar located on the transmembrane IICMan-IIDMan complex.
 
 
 
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