Substrate-induced conformational change in yeast hexokinase. Click on the images at the right to switch between conformations. In the bound state (Fig. 15-2b, click the 'On' button to highlight the residues involved in substrate binding. (a) Ribbon diagram of a hexokinase subunit showing the prominent bilobal appearance of the free enzyme (the large domain is purple and the small domain is yellow). (b) Model of the hexokinase complex with glucose drawn in space-filling form with C green and O red; the domains have swung together to engulf the substrate. Clicking the "Show Animation" button shows an animation of the structural changes between the two conformations, initially with the protein and glucose shown as in Parts a and b. Clicking on the "Spheres" button shows the space-filling form with small domain C yellow, large domain C purple, N blue, O red, and S gold. Clicking on the "Backbone" button shows the animated protein in worm form colored in rainbow order from its N-terminus (blue) to its C terminus (red). [Based on an X-ray structure by Igor Polikarpov, Instituto de Fisica em Sao Carlos, Brazil. PDids 1IG8 and 3B8A.]