Howto export animated cube to MD2?

I’ve an animated cube and tried now several ways of animation but the animation is always lost on a MD2 export.
As I’ve seen in this forum that it should work somehow. But how?
What are the important steps that the md2 exporter recognizes the animation?

I’ve uploaded my cube blend to:
Perhaps someone can try and modify it so that export to md2 implements an animation which can be reimported to blender again.

Thanks for your help.