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Figure 2.
Figure 2. (A) Closed conformation and ApoA. Superposition
of ApoA (black) and C:AlF:SP20 (green),[9] in the open and
closed conformations, respectively. Broken lines show the
distances of two representative parts of the small lobe; the
Gly-rich loop (Ser53 C^a) and the C-terminal tail (Ser339 C^a).
Residues 128-300 were superimposed. (B) Intralobe hydrophobic
contacts. The hydrophobic patch between the small and large
lobes, which may provide the "grease" for the shearing motion
associated with domain rotation, is shown. Glu91, a conserved
residue in the C helix (C), which is important for orienting the
phosphate groups of ATP during phosphoryl transfer, is preformed
and is within hydrogen-bonding distance from the amide hydrogen
atom of Phe185 in the large lobe. From the small lobe (gold
ribbon) are residues Glu91, Ile94, Val98, Phe100, Phe102,
Leu103, and Val104 (side-chains, blue). From the large lobe, the
residues shown are Thr153, Tyr156, Leu162, Tyr179, Gln181, and
Phe185 (side-chains, pink). Residues that come into close
contact are Ile94-Leu162, Phe185; Val98, Phe100 and
Leu103-Tyr156, Leu103-Phe185, and Val104-Gln181. Other hydrogen
bonding pairs are: Asn99 amide group to Tyr156 hydroxyl group,
and Val104 amide hydrogen atom to Val182 carbonyl oxygen atom.
The gray ribbon represents the E helix (E) and the black ribbon
includes the Mg-positioning loop (Mg), both from the large lobe.
Helix A (A) is shown, since Phe18, Ala22, and Phe26 contribute,
peripherally.
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