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Figure 5.
Figure 5. Structural details of AAA binding in the crystal
structure. (a) Stereo view of (2F[o] -F[c]) electron density map
contoured at the 1s level around the AAA binding sites. Carbon
atoms of the AAAs are colored magenta while AAAs and methionine
residues are labeled. (b) Comparison of the binding sites of AAA
molecules. AAA1 (left) and AAA2 (right) (lines and circles) are
shown with the interacting protein residues (lines). The
orientation of CaM is changed between the left and right panels
by fitting backbone atoms of the two domains onto each other
considering the similar fold of those. The accommodations and
conformations of the two AAAs are very similar. (c) The backbone
conformation of CaM colored from the N-terminal to the
C-terminal from blue to red with the two bound AAA molecules.
(d) Comparison of the P3[2]21 crystal structure (red) with the
P1 structure (green). The conformation of AAA changes upon the
domain motion of CaM. AAA2 and the interacting helices of the
N-terminal domain are shown with the C^a atoms of residues 92 to
144 fitted together. The molecular surface of the C-terminal
hydrophobic pocket of CaM, calculated by GRASP [Nicholls et al
1991], is shown as a chicken-wire representation (blue). The
most important interactions between AAA and CaM, shown only for
P3[2]21, are emphasized with yellow shaded lines. The black
arrow shows the change in conformation of AAA2 following the
domain motion of CaM. (a) Drawn with Bobscript v2.3 [Esnouf
1997] and (b), (c) and (d) with MOLSCRIPT v2.1 [Kraulis 1991].
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