Molecule of the Month: Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
Cells salvage and recycle their obsolete DNA and RNA
Perils of Purines
Purines and Parasites
Exploring the Structure
HGPRT (PDB entries 1z7g, 1d6n, 1bzy and 1hmp)
HGPRT performs its reaction in several steps. First, an activated form of the sugar binds, followed by the purine base. The enzyme then connects the two, releasing a pyrophosphate molecule. Finally, the nucleotide is released in the slowest step of the whole process. Researchers have captured the enzyme performing several of these steps, including the empty enzyme (PDB entry 1z7g ), the enzyme with the sugar and base in the active site (PDB entry 1d6n ), a complex with an analog of the transition state (shown here from PDB entry 1bzy ), and a form with the final product in the active site before release (PDB entry 1hmp ). A large loop (shown here in turquoise) opens and closes around the active site during the reaction. To explore these structures, click on the image for an interactive Jmol.
Topics for Further Discussion
- You can use the Compare Structures feature at the RCSB PDB to overlap and compare the structures of HGPRT from human cells and from malaria. The structures in the Jmol were also overlapped with this feature to show the motion of the loop.
- Complexes of HGPRT with several potential anti-malarial drugs are included in the PDB. You can compare these with the structures of the substrates and products of the enzyme.
July 2012, David Goodselldoi:10.2210/rcsb_pdb/mom_2012_7