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Figure 1.
Figure 1. Comparison of the Fold of Autoinhibited CaM
Kinase I with cAPK(A) Ribbon drawing of CaM kinase I (CaMKI;
left) and cAPK (right). The structures of autoinhibited CaMKI
and cAPK are drawn with their C-terminal lobes (helical domain
at bottom) in similar orientations. The cAPK structure is
that of [69], with the PKI peptide inhibitor colored orange and
the ATP shown in ball and stick form (entry 1ATP in the
Brookhaven Protein Data Bank). cAPK has its two domains in a
closed conformation whereas the CaMKI active site is opened
by an 18° relative rotation of the domains, with respect to
cAPK. The regulatory C-terminal sequence of CaMKI, containing
the autoinhibitory region, is colored red (residues 285–316).
The ATP-binding glycine-rich loop or P loop (colored green in
both structures; residues 23–36 in CaMKI, 46–59 in cAPK)
covers the ATP molecule in cAPK. In CaMKI, the P loop interacts
with the autoinhibitory region and adopts a distinct
conformation that distorts the ATP-binding site. Two
disordered regions of CaMKI in the crystal structure are
indicated with dotted lines (ten residues, 54–63, not modeled
in the N-terminal domain, and eighteen residues, 164–181, in
the C-terminal domain, are indicated by the corresponding number
of dots). The region of CaM kinase I that is boxed is shown in
detail in (B).(B) Stereo-diagram showing the interaction between
the CaMKI regulatory segment (red, residues 285–316) and the
catalytic core of the enzyme (gray). Selected residues of the
regulatory region are drawn in white, and residues from the
catalytic core are colored blue. Figure prepared using the
programs MOLSCRIPT ([41]) and Raster3D ( [2]).
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