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Figure 3.
Figure 3. Peptide titrations of Ca^2+-loaded calbindin-D[28K]
and binding interface. (a–c) Selected regions of the 2D
^1H[N]-^15N TROSY spectra of calbindin-D[28K] binding to target
peptides from (a) RanBPM (LASIKNR), (b) IMPase (ISSIKEKYPSHS)
and (c) the pro-domain of procaspase-3 (SKSIKNLEP). The spectra
were collected at peptide/protein ratios of 0:1 (black), 1:1
(green), 2:1 (dark blue), 4:1 (light blue), 8:1 (red) and 16:1
(pink). Residues showing chemical shift changes or line
broadening are affected by peptide binding. (d) RanBPM peptide
binding characteristics mapped onto the structure ensemble of
Ca^2+-loaded calbindin-D[28K], displayed as a PyMOL surface
plot. Residues are highlighted according to trends observed as
results of the peptide titration: red, peak linewidth broadening
and disappearance; yellow, substantial change in chemical shift;
blue, moderate linewidth broadening and change in chemical
shift; gray, residues unobservable at 25 °C owing to
conformational exchange on an intermediate NMR timescale.
Peptides derived from IMPase and procaspase-3 show similar
binding traits (see text).
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