Example from the page HMG-CoA Reductase:
The HMG binding pocket is the site of catalysis in HMGR. The “cis-loop” that bends over the top of HMG is a critical structural element of this binding site. Residues E559 and D767 and are positioned in the active site as is K691 which is only 2.7 angstroms from the HMG O2 carbonyl oxygen. It is this K691 that likely stabilizes the negatively charged oxygen of the first mevaldyl-CoA intermediate. The mevaldyl CoA intermediate is subsequently converted to Mavaldehyde with added stabilization from H866, which is within hydrogen bonding distance of the thiol group. It is then believed that the close proximity of E559 and D767 increases the pKA of E559, allowing it to be a proton donor for the reduction of mevaldehyde into mevalonate.
Compared with:
The HMG binding pocket is the site of catalysis in HMGR. The“cis-loop” that bends over the top of HMG is a critical structural element of this binding site. Residues E559 and D767 and are positioned in the active site as is K691 which is only 2.7 angstroms from the HMG O2 carbonyl oxygen. Etc…