1. A binding site for the coenzyme (NAD⁺ or NADH).
2. And a binding site for the substrate (pyruvate or lactate).

The coenzyme binding domain is made up of six strands of parallel beta-sheets(blue arrows).

The coenzyme binds near the end of the parallel sheets in an extended conformation.

The postition of the coenzyme binding site(blue) coincides with a groove at either end of the molecule.This groove can be clearly seen when looking at the coenzyme binding site from the side. The coenzyme(red) fits in the apex of this groove.

Binding of the coenzyme causes Arg 101(green) to take a closed conformation and cover the coenzyme. Normally when the coenzyme is not bound this residue would be sticking out into the solvent. The role of Arg 101 will be talked about more in the mechanism section. Here you can see it in this closed conformation.