1JLR

STRUCTURE OF THE URACIL PHOSPHORIBOSYLTRANSFERASE GTP COMPLEX 2 MUTANT C128V

Summary for 1JLR

• Entry DOI: 10.2210/pdb1jlr/pdb
• Related: 1BD3 1BD4 1UPF 1UPU
• Descriptor: Uracil Phosphoribosyltransferase, PHOSPHATE ION, GUANOSINE-5'-TRIPHOSPHATE, ... (4 entities in total)
• Functional Keywords: transferase, glycosyltransferase, uprtase, gtp activated, tetramer
• Biological source: Toxoplasma gondii
• Total number of polymer chains: 4
• Total formula weight: 113085.47

Authors

Schumacher, M.A.,Bashor, C.J.,Otsu, K.,Zu, S.,Parry, R.,Ulmman, B.,Brennan, R.G. (deposition date: 2001-07-16, release date: 2002-01-10, Last modification date: 2023-08-16)

Primary citation

Schumacher, M.A.,Bashor, C.J.,Song, M.H.,Otsu, K.,Zhu, S.,Parry, R.J.,Ullman, B.,Brennan, R.G.
The structural mechanism of GTP stabilized oligomerization and catalytic activation of the Toxoplasma gondii uracil phosphoribosyltransferase.
Proc.Natl.Acad.Sci.USA, 99:78-83, 2002

PubMed Abstract: Uracil phosphoribosyltransferase (UPRT) is a member of a large family of salvage and biosynthetic enzymes, the phosphoribosyltransferases, and catalyzes the transfer of ribose 5-phosphate from alpha-d-5-phosphoribosyl-1-pyrophosphate (PRPP) to the N1 nitrogen of uracil. The UPRT from the opportunistic pathogen Toxoplasma gondii represents a promising target for rational drug design, because it can create intracellular, lethal nucleotides from subversive substrates. However, the development of such compounds requires a detailed understanding of the catalytic mechanism. Toward this end we determined the crystal structure of the T. gondii UPRT bound to uracil and cPRPP, a nonhydrolyzable PRPP analogue, to 2.5-A resolution. The structure suggests that the catalytic mechanism is substrate-assisted, and a tetramer would be the more active oligomeric form of the enzyme. Subsequent biochemical studies revealed that GTP binding, which has been suggested to play a role in catalysis by other UPRTs, causes a 6-fold activation of the T. gondii enzyme and strikingly stabilizes the tetramer form. The basis for stabilization was revealed in the 2.45-A resolution structure of the UPRT-GTP complex, whereby residues from three subunits contributed to GTP binding. Thus, our studies reveal an allosteric mechanism involving nucleotide stabilization of a more active, higher order oligomer. Such regulation of UPRT could play a role in the balance of purine and pyrimidine nucleotide pools in the cell.

PubMed: 11773618
DOI: 10.1073/pnas.012399599

Experimental method

X-RAY DIFFRACTION (2.45 Å)