1QK4

TOXOPLASMA GONDII HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE IMP COMPLEX

Summary for 1QK4

• Entry DOI: 10.2210/pdb1qk4/pdb
• Related: 1DBR 1HMP 1QK3 1QK5
• Descriptor: HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE, INOSINIC ACID (3 entities in total)
• Functional Keywords: transferase, glycosyltransferase, purine salvage
• Biological source: TOXOPLASMA GONDII
• Total number of polymer chains: 4
• Total formula weight: 108214.83

Authors

Heroux, A.,White, E.L.,Ross, L.J.,Borhani, D.W. (deposition date: 1999-07-09, release date: 1999-10-17, Last modification date: 2023-12-13)

Primary citation

Heroux, A.,White, E.L.,Ross, L.J.,Borhani, D.W.
Crystal Structures of the Toxoplasma Gondii Hypoxanthine-Guanine Phosphoribosyltransferase Gmp and -Imp Complexes: Comparison of Purine Binding Interactions with the Xmp Complex
Biochemistry, 38:14485-, 1999

PubMed Abstract: The crystal structures of the guanosine 5'-monophosphate (GMP) and inosine 5'-monophosphate (IMP) complexes of Toxoplasma gondii hypoxanthine-guanine phosphoribosyltransferase (HGPRT) have been determined at 1.65 and 1.90 A resolution. These complexes, which crystallize in space groups P2(1) (a = 65.45 A, b = 90.84 A, c = 80. 26 A, and beta = 92.53 degrees ) and P2(1)2(1)2(1) (a = 84.54 A, b = 102.44 A, and c = 108.83 A), each comprise a tetramer in the crystallographic asymmetric unit. All active sites in the tetramers are fully occupied by the nucleotide. Comparison of these structures with that of the xanthosine 5'-monophosphate (XMP)-pyrophosphate-Mg(2+) ternary complex reported in the following article [Héroux, A., et al. (1999) Biochemistry 38, 14495-14506] shows how T. gondii HGPRT is able to recognize guanine, hypoxanthine, and xanthine as substrates, and suggests why the human enzyme cannot use xanthine efficiently. Comparison with the apoenzyme reveals the structural changes that occur upon binding of purines and ribose 5'-phosphate to HGPRT. Two structural features important to the HGPRT mechanism, a previously unrecognized active site loop (loop III', residues 180-184) and an active site peptide bond (Leu78-Lys79) that adopts both the cis and the trans configurations, are presented.

PubMed: 10545170
DOI: 10.1021/BI990507Q

Experimental method

X-RAY DIFFRACTION (1.9 Å)