Figure 12.

Structural model for the molecular basis of lysine-265 mutation-mediated effects on the allosteric pathway. (a) Overview picture of the myosin motor domain depicting the location of K265 in the rigor-like structures of Dd myosin-2 (blue, pdb: 2AKA)²³ and of G. gallus myosin-5a (red, pdb: 1OE9)²⁴. Note the completely closed actin-binding cleft in the myosin-5a structure and the partially closed cleft in myosin-2, which is proposed to close completely upon binding to F-actin. (b) Close-up view of the actin-binding cleft near K265 (Dd myosin-2) and K246 (Gg myosin-5a). (c) Schematic representation of the allosteric branching point K265/D590/Q633. The K265-Q633 interaction is established in the rigor state with closed actin-binding cleft. Red numbers indicate interaction distances in Å. The numbers in parentheses are distances proposed for the position of Gln633 in Dd myosin-2 with completely closed actin binding cleft (based on myosin-5a, pdb: 1OE9). (d–f) Illustration of the effects of mutations K265A, K265Q and K265E. Note the complete absence of interactions for Ala265, the repulsion between Glu265 and Asp590 and the retained Gln633 interaction of Gln265. (g) Schematic representation of interactions in the PBP binding pocket of WT Dd myosin-2 (based on pdb: 2JHR)⁹. (h) Mutation K265E eliminates specific interactions and thereby weakens the interaction network of PBP.