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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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