Figure 2.

Flexible superposition of AK TSA on the substrate-free form. Two rounds of selection eliminated the 75% least consequential dihedrals. Refinement continued for 200 cycles with an ${\ell }^1$-norm λ = 5. (A) Changes in pseudo-torsion angles. Annotation includes: dynamic domain designation (Hayward and Lee, 2002; Niu et al., 2011); observation of NMR relaxation exchange (R_ex, wide arrows) in the substrate-free (Davulcu et al., 2009) or –bound (this work) states; and NMR chemical shift perturbation (Δδ, thin arrows) between substrate-free and -bound forms, excluding residues close to substrates. (B) Starting from the AK TSA structure (orange), the parsimoniously superposed model (color- and thickness-coded by magnitude of pseudo-dihedral rotation, blue to red) is now well fit to the substrate-free form (green). Transition state analogs are shown as a stick model. Side chains are shown for residues with backbone nitrogen R_ex to highlight proximity to changing dihedrals. (See also Figure S5) (C) The TSA and superposed structures are rotated 90° to highlight flexing of the β-sheet.