Virtuelle (Nano) Welten: PDB Molecule of the Month 30: Glutamin Synthetase

Two Doors

Each of the twelve active sites of glutamine synthetase has two metal ions, either magnesium or manganese (shown here in purple), bound at the center of a tunnel. The substrates enter from two sides of the tunnel: ATP enters on the exposed faces on the top and bottom of the enzyme (ATP is easily seen in the upper picture on the previous page) and glutamate and ammonia squeeze through an opening between the upper ring of subunits and the lower ring. This structure, PDB entry 1fpy, contains a ADP molecule bound in the ATP site, two manganese ions (which bind tighter than magnesium, but make the enzyme slightly slower), and an inhibitor that is about the same size and shape as glutamine.

Glutamine Synthetase

Two Doors