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Figure 4.
Reshaped active site in the tetrameric structure. A, the
substrate cleft is covered with lid 1 (aa 92-97; purple) and lid
2 (aa 315-322; cyan) generated by the tetrameric arrangement.
The N-terminal domain is shown in blue. The glucose and acarbose
intermediate ligands in the complex structure are superposed and
indicated by sticks. The flexible loop (aa 399-416) is orange.
B, the conformational change in the flexible loop results in a
shift of Glu^399 and Tyr^408 away from the other catalytic
residues Asp^363 and Asp^471. The region in the comparison is
blue for the dimeric structure and orange for the tetramer. C,
the active sites (black circles) highlighted by the superposed
ligands are seen along the connected substrate-binding grooves
inside the tetramer. mole, molecule.
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