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Figure 2.
Summary of the spectral perturbations for integrin
β[3]/skelemin and α[IIb]/skelemin interactions. All
experiments were performed in 0.25× PBS (pH 6.2) buffer at
25 °C. A, expanded region of HSQC spectra of ^15N-labeled
β[3] tail in the absence (black) and presence of the unlabeled
skelemin IgC45 at different ratios: 1:1, green; 1:3, red; 1:5,
blue. Residues labeled indicate the most significant changes. B,
chemical shift changes of the β[3] tail upon SkIgC45 binding.
Bars are colored according to the different ratios as presented
in A. First nine residues (Lys^716-Arg^724) in 1:5 (blue) series
are undetectable because of extreme line-broadening and are
shown as bars with maximum values. C, chemical shift changes of
the β[3] tail upon binding to different skelemin constructs at
the ratio of 1:3. Bars are colored according to the interaction
with a particular domain of skelemin: green bars, interaction
with SkIgC4; blue bars, interaction with SkIgC5; red bars,
interaction with SkIgC45. The last bar in each series represents
chemical shifts of the Trp^739 side-chain HN; His^722 is
undetectable (probably because of the exchange with water) and
is not shown in green and blue series. Δδ(HN,N) in ppm refers
to the combined HN and N chemical shift changes, according to
the equation: Δδ(HN,N) = ((Δδ[HN]^2 + 0.2
(Δδ[N])^2)[½], where Δδ = δ[bound] - δ[free]. D,
HSQC spectra of ^15N/^2H-labeled skelemin IgC45 in the absence
(black) and presence (red) of the unlabeled β[3] tail. E, HSQC
spectra of ^15N-labeled α[IIb] in the absence (black) or
presence (red) of unlabeled SkIgC45 at the ratio of 1:5.
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