Figure 6.

Analysis of the Interdomain Motions and of Their Coupling to Intradomain Structural Changes

(A) Position of the vector representing the axis of helix IV and V in the Ca²⁺-CaM ensemble on a unit sphere. The Cα atom of residue 79 (in the middle of the flexible linker of CaM) is placed at the center of the sphere. The position of helix V, on which structures were aligned (i.e., fixed), is shown as a black diamond, and that of helix IV in the crystal structure of Ca²⁺-CaM and the crystal structure of CaM-MLCK are indicated by a red square and diamond, respectively. The positions of helix IV in the Ca²⁺-CaM ensemble are indicated by green dots; those found in different CaM complexes are indicated by additional diamonds (fully Ca²⁺ loaded) and crosses (partially loaded) (for details, see Figure S8).

(B) Distribution of the axis of helix IV in the Ca²⁺-CaM ensemble in polar coordinates. The positions found in the structures of CaM complexes are indicated as in (A).

(C) Position of the vector representing the axis of helix IV and V in the CaM-MLCK ensemble on a unit sphere.

(D) Distribution of the axis of helix IV in the CaM-MLCK ensemble in polar coordinates.

(E–H) Interhelical angles in the Ca²⁺-CaM ensemble as a function of the CαRMSD from the crystal structure of CaM-MLCK. The average, smallest, and largest angles of each bin are shown in black, red, and green, respectively. Interhelical angles I-II, III-IV, V-VI, and VII-VIII are shown in (E), (F), (G), and (H), respectively.

(J and K) Interhelical angles V-VI and VII-VIII, respectively, as a function of the interdomain position of helix IV in the Ca²⁺-CaM ensemble. The position of the helix is calculated as in (B).