Introduction - This script shows the conformational change, "induced fit", that results from glucose binding to hexokinase.
Scroll down until the text corresponding to the view is visible. (Based on 2yhx.pdb, C.M.Anderson et al. J. Mol. Biol. 123 15 (1978) and 1hkg.pdb, W.S.Bennett & T.A.Steitz Philos. Trans.R.Soc.London 293 43 (1981)).

This is hexokinase without its substrate, glucose. Notice the open cleft.

 This is hexokinase with glucose (RED) bound in the active site. Notice how the cleft closed when the enzyme bound glucose.