You are correct. Protein chirality determines which direction they twist when they fold but the binding sites are all made up of the same functional groups, jus

You are correct. Protein chirality determines which direction they twist when they fold but the binding sites are all made up of the same functional groups, just arranged differently. Realistically they have to be compatible because chirality is enforced by a D-handed chiral checkpoint protein that preferentially binds to L-amino acids, excluding the D-amino acids. All living organisms use the “wrong” isomer to make sure only the “right” isomer is used in protein synthesis. The amino acid cysteine is also present in both forms in mammals, so it extends to small molecules too.