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PDBsum entry 1vrc
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References listed in PDB file
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Key reference
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Title
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Solution nmr structure of the 48-Kda iiamannose-Hpr complex of the escherichia coli mannose phosphotransferase system.
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Authors
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D.C.Williams,
M.Cai,
J.Y.Suh,
A.Peterkofsky,
G.M.Clore.
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Ref.
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J Biol Chem, 2005,
280,
20775-20784.
[DOI no: ]
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PubMed id
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Abstract
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The solution structure of the 48-kDa IIA(Man)-HPr complex of the mannose branch
of the Escherichia coli phosphotransferase system has been solved by NMR using
conjoined rigid body/torsion angle-simulated annealing on the basis of
intermolecular nuclear Overhauser enhancement data and residual dipolar
couplings. IIA(Man) is dimeric and has two symmetrically related binding sites
per dimer for HPr. A convex surface on HPr, formed primarily by helices 1 and 2,
interacts with a deep groove at the interface of the two subunits of IIA(Man).
The interaction surface on IIA(Man) is predominantly helical, comprising helix 3
from the subunit that bears the active site His-10 and helices 1, 4, and 5 from
the other subunit. The total buried accessible surface area at the
protein-protein interface is 1450 A(2). The binding sites on the two proteins
are complementary in terms of shape and distribution of hydrophobic,
hydrophilic, and charged residues. The active site histidines, His-10 of
IIA(Man) and His-15 (italics indicate HPr residues) of HPr, are in close
proximity. An associative transition state involving a pentacoordinate
phosphoryl group with trigonal bipyramidal geometry bonded to the N-epsilon2
atom of His-10 and the N-delta1 atom of His-15 can be readily formed with
negligible displacement in the backbone coordinates of the residues immediately
adjacent to the active site histidines. Comparing the structures of complexes of
HPr with three other structurally unrelated phosphotransferase system proteins,
enzymes I, IIA(glucose), and IIA(mannitol), reveals a number of common features
that provide a molecular basis for understanding how HPr specifically recognizes
a wide range of diverse proteins.
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Figure 5.
FIG. 5. The IIA^Man-HPr interface. A, stereoview of the
interface with the backbone shown as tubes (green, HPr; blue,
subunit A of IIA^Man; red, subunit B of IIA^Man) and the side
chains as bonds (light green, HPr; cyan, subunit A of IIA^Man;
pink, subunit B of IIA^Man; purple, active site histidines).
Residues of HPr are labeled in italics. Note that the  1-ppm
chemical shift perturbation observed for the backbone amide of
Ser-72 of IIA^Man (cf. Fig. 1) is because of a ring current
shift arising from its close proximity ( 3.9 Å) to the
imidazole ring of His-15 of HPr. No other backbone amide proton
of IIA^Man is within 5.7 Å of an aromatic side chain of
HPr. B, diagrammatic summary of interfacial contacts.
Residuesinvolved in potential electrostatic, hydrogen-bonding,
or water-mediated hydrogen-bonding interactions are indicated in
red (side chain-side chain contacts), blue (side chain of HPr to
backbone carbonyl of IIA^Man), or green (side chain of IIA^Man
to backbone carbonyl of HPr). The active site histidines are
shown in purple. C, interaction surface on IIA^Man for binding
HPr. D, interaction surface on HPr for binding IIA^Man. Residues
in the interaction surfaces (C and D) are color-coded as
hydrophobic (green), hydrophilic (cyan), positively charged
(blue), or negatively charged (red). The relevant portions of
the backbone of the interacting partner, HPr in C (gold) and
IIA^Man in D (lilac for subunit A, gold for subunit B,) are
displayed as tubes. In C, the surface of the non-interacting
residues of IIA^Man is colored in dark gray for subunit A and
light gray for subunit B. Residues of HPr are labeled in italics.
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Figure 6.
FIG. 6. Comparison of the relative orientation of the
interacting helices in the IIA^Man-HPr and EIN-HPr complexes.
The two complexes have been best-fitted to the coordinates of
HPr. Two approximately orthogonal views are shown with the
helices of HPr (  1 and 2) in
green; helices 1, 4, and 5 of
subunit B of IIA^Man in red; helix 3 of subunit A of
IIA^Man in blue; and helices 2, 2', 3, and 4 of EIN
in gold. The coordinates of the EIN-HPr complex are taken from
Ref. 5 (Protein Data Bank accession code 3EZA [PDB]
).
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The above figures are
reprinted
from an Open Access publication published by the ASBMB:
J Biol Chem
(2005,
280,
20775-20784)
copyright 2005.
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