same complex, different binding mode

Dr Engelbert Buxbaum engelbert_buxbaum at
Mon Jul 5 17:39:47 EST 2004

Boris Gorelik wrote:

> Hello,
> Can someone point me to refference/PDB codes of known protein ligand
> structures where the ligand and the protein are the same, but the ligand
> exhibits different binding modes?

This would occur for example in cooperative enzymes with homotropic
regulators. The most well known example is haemoglobin (an enzyme
/honoris causa/), whose transition between T- and R-conformation is
induced by oxygen binding.

Another case would be transferrin, which has 2 non-identical,
non-cooperative (very unusual!) binding sites for iron.

A third example would be P-type transmembrane ATPases (Na/K-ATPase in
animal cell membranes, Ca-ATPase in sarcoplasmic reticulum, H/K-ATPase
in stomach parietal cells and a couple of others), which cycle between 2
conformations, E1 with high and E2 with low affinity for ATP.

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