1AK5

INOSINE MONOPHOSPHATE DEHYDROGENASE (IMPDH) FROM TRITRICHOMONAS FOETUS

Summary for 1AK5

• Entry DOI: 10.2210/pdb1ak5/pdb
• Descriptor: INOSINE-5'-MONOPHOSPHATE DEHYDROGENASE, SULFATE ION (3 entities in total)
• Functional Keywords: dehydrogenase, alpha-8-beta-8 barrel, tim barrel, purine metabolism, oxidoreductase, tetramer, c4-tetramer
• Biological source: Tritrichomonas foetus
• Total number of polymer chains: 1
• Total formula weight: 55636.08

Authors

Whitby, F.G. (deposition date: 1997-05-28, release date: 1997-09-17, Last modification date: 2011-07-13)

Primary citation

Whitby, F.G.,Luecke, H.,Kuhn, P.,Somoza, J.R.,Huete-Perez, J.A.,Phillips, J.D.,Hill, C.P.,Fletterick, R.J.,Wang, C.C.
Crystal structure of Tritrichomonas foetus inosine-5'-monophosphate dehydrogenase and the enzyme-product complex.
Biochemistry, 36:10666-10674, 1997

PubMed Abstract: Inosine-5'-monophosphate dehydrogenase (IMPDH) is an attractive drug target for the control of parasitic infections. The enzyme catalyzes the oxidation of inosine monophosphate (IMP) to xanthosine monophosphate (XMP), the committed step in de novo guanosine monophosphate (GMP) biosynthesis. We have determined the crystal structures of IMPDH from the protozoan parasite Tritrichomonas foetus in the apo form at 2.3 A resolution and the enzyme-XMP complex at 2.6 A resolution. Each monomer of this tetrameric enzyme is comprised of two domains, the largest of which includes an eight-stranded parallel beta/alpha-barrel that contains the enzyme active site at the C termini of the barrel beta-strands. A second domain, comprised of residues 102-220, is disordered in the crystal. IMPDH is expected to be active as a tetramer, since the active site cavity is formed by strands from adjacent subunits. An intrasubunit disulfide bond, seen in the crystal structure, may stabilize the protein in a less active form, as high concentrations of reducing agent have been shown to increase enzyme activity. Disorder at the active site suggests that a high degree of flexibility may be inherent in the catalytic function of IMPDH. Unlike IMPDH from other species, the T. foetus enzyme has a single arginine that is largely responsible for coordinating the substrate phosphate in the active site. This structural uniqueness may facilitate structure-based identification and design of compounds that specifically inhibit the parasite enzyme.

PubMed: 9271497
DOI: 10.1021/bi9708850

Experimental method

X-RAY DIFFRACTION (2.3 Å)