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Figure 2.
FIG. 2. X-ray structures of the complexes  [L] I
domain/LFA703 and [L] I domain/LFA878. A,
stereo image of the L-site for [L] I domain/LFA703. I
domain residues and ribbon representation are in white, LFA703
in cyan (oxygens are red, and nitrogens are blue). The
substituted naphthyl group of LFA703 occupies a region (the
naphthyl subpocket, colored magenta) formed mainly by Val130,
Thr231, Val233, and Ile^255. B, stereo image of the L-site for
[L]
I domain/LFA878 (coloring as for LFA703). The veratryl group of
LFA878 occupies a region (the veratrylsubpocket, colored
magenta) formed mainly by Tyr257, Glu284, and Phe^285. A
comparison with the I domain/LFA703 complex shows that Glu284
has dramatically changed its side-chain conformation. C, F[o] -
F[c] electron density (contour level 3  , 8-2.2 Å) before
LFA703 was inserted into the model. Superposed is the final
model of LFA703 (carbons are cyan/yellow, oxygens are red, and
nitrogens are blue). The naphthyl group adopts two alternate
conformations. D, F[o] (contour - F[c] density level 3 electron
,
8-2.1 Å) before LFA878 was inserted into the model.
Superposed is the final model of LFA878 (coloring as for
LFA703). E, superposition of LFA703 (carbons are yellow), LFA878
(carbons are cyan), and lovastatin (carbons are white) using C
atoms of the respective
[L]
I domains. The decalin moieties occupy practically identical
positions. F, MIDAS site for [L] I domain/LFA703.
Final 2F[o] - F[c] electron density (contour level 3 , 8-2.2
Å) is shown in blue; carbons are yellow, oxygens are red,
nitrogens are blue, water molecules are white, and the Mg2+ ion
is cyan. Selected hydrogen bonds are shown as black lines
(dashed lines for the interaction with neighboring molecule).
Because of the direct coordination by Asp239, the
electrophilicity of Mg2+ is reduced so that a glutamate (Glu218,
colored magenta) from a neighboring molecule is only interacting
indirectly (via a water molecule) with the Mg2+ in the MIDAS
site. Single letter amino acid abbreviations are used with
position numbers throughout the figure.
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