FlexiFit
A binding pocket is often drawn as a rigid keyhole waiting for exactly one key. Real pockets are usually softer than that: a ligand is jostled in, and when a shape fits it sticks — and the pocket often reshapes around it (this is called induced fit). Predict, for each real enzyme, whether its pocket is a rigid keyhole or reshapes on contact, then watch the motion. Everything runs locally; nothing about you is collected.
This is the tool. The enzymes are listed below (works without JavaScript). A native version, when it ships, adds offline use; it never gates the web.
Loading the game… If it does not start, the guide below still works.
How to play. Press Start. Predict Rigid keyhole or Reshapes on contact (buttons or keys 1/R, 2/F). The real motion is revealed and your call is scored. Press Enter or Next. There is no way to lose.
Why pockets are not rigid keyholes
The old "lock and key" picture says a pocket is a fixed slot for one exact key. Often it is closer to a hand closing around an object: a ligand is jostled into the neighbourhood, a shape fits and sticks, and the pocket reshapes to grip it (induced fit). Lock-and-key does happen, but the rigid-keyhole picture is the oversimplification this game corrects — misconception M02.
The enzymes
| Enzyme | Binds | How the pocket reshapes |
|---|---|---|
| Hexokinase HK1 · P19367 | glucose | Two lobes swing shut around glucose. |
| Adenylate kinase AK1 · P00568 | ATP / AMP | LID + NMP domains fold down over the nucleotides. |
| Dihydrofolate reductase DHFR · P00374 | folate + NADPH | Active-site loops shift through the cycle. |
| Calmodulin CALM1 · P0DP23 | a target helix | Wraps both lobes around the target. |
Methods & about
This is a teaching game and a simplification. All four exemplars are well-documented induced-fit / conformational-change binders; lock-and-key binding also exists, but induced fit is the common case the "rigid keyhole" picture misses. Structures are the real AlphaFold predictions, shown for context (the single model does not animate the closure). No score history, no accounts, nothing sent anywhere.
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