The interaction between the PBD and LD peptides. a and
b, overlay of GIT1 PBD spectra titrated with LD4 and LD2 peptides,
respectively. Blue, GIT1 PBD alone; cyan, adding 0.5 eq of
ligand; green, adding 1 eq of ligand; gold, adding 2 eq of
ligand; red, adding 5 eq of ligand. Arrows mark
significantly perturbed resonance, and dashed arrows mark
perturbation with intermediate exchange rate. c, sequence alignment
of human LD2 and LD4 peptides used in this study. Identical residues are
marked with asterisks, and the LDXLLXXL motif is
shown in bold. Conventional nomenclature is used; the first Leu is
Φ0, and other residues are named as in the figure. d and
e, composite chemical shift perturbation plotted against residue
number for LD4 and LD2, respectively. Composite chemical shift perturbation
was calculated by the equation Δδcomposite =
(ΔδNH2 +
ΔδN2/25)1/2. Lys663,
Lys758, Gln, and Tyr751 are labeled, and they are among
those dramatically shifted peaks.