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Figure 3.
Fig. 3. Albumin binding site of ALB8-GA and G148-GA3.
Panel A, chemical shift perturbations upon addition of 0.6 eq of
rabbit serum albumin to ALB8-GA at 37 °C. Panel B, same as
panel A but for G148-GA3. The chemical shift change was
calculated from the chemical shift of the backbone 15N and 1H
resonances using the following formula:   = (( (1H))2 +
(0.2 (15N))2)1/2
and is indicated with a filled bar at the corresponding residue.
Each residue for which the cross-peak is broadened beyond
detection upon the addition of albumin is indicated by a green
bar at the value of 0.14 ppm (corresponding to the maximum
chemical shift change of residues with nonbroadened
cross-peaks). Residues that were too weak to give any reliable
information, overlapped, or were not detected at all are
indicated with outlined circles at a value of 0 ppm. The helices
are indicated by boxes at the top. Panel C, overlay of a region
of 15N-1H HSQC spectra of 2 mM ALB8-GA at 47 °C in the
absence (blue) and in the presence (red) of 1 eq of rabbit serum
albumin with the residue numbers indicated. For details, see
"Results and Discussion." Panels D and E, contact surfaces
displaying the effects of albumin binding shown in two different
views differing by a 180° rotation along the y axis. The
orientation of the views to the left is the same as in the
ribbon representations in Fig. 2, panels C and B, respectively.
The 18 (ALB8-GA, panel D) and 20 (G148-GA3, panel E)
significantly perturbed residues are indicated in red. Residues
that were too weak to give any reliable information, overlapped,
or were not detected at all are shown in magenta. The remaining
residues are colored blue. To clarify the presentation, only
residues belonging to the defined GA module sequence are shown.
The contact surfaces in panels D and E were prepared using
MOLMOL (40).
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