Interactions of GTP with the ATP-grasp Domain of GTP-specific Succinyl-CoA Synthetase

• Published in: The Journal of biological chemistry 2006-04, Vol.281 (16), p.11058-11065
• Main Authors: Fraser, Marie E., Hayakawa, Koto, Hume, Millicent S., Ryan, David G., Brownie, Edward R.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - chemistry; Animals; Arginine - chemistry; Binding Sites; Crystallography, X-Ray; Glutamine - chemistry; Guanine - chemistry; Guanosine Triphosphate - chemistry; Guanosine Triphosphate - metabolism; Histidine - chemistry; Hydrolysis; Models, Molecular; Nitrogen - chemistry; Phosphates - chemistry; Phosphorylation; Promoter Regions, Genetic; Protein Binding; Protein Conformation; Protein Isoforms; Ribose - chemistry; Succinate-CoA Ligases - chemistry; Succinate-CoA Ligases - metabolism; Swine
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M511785200

Two isoforms of succinyl-CoA synthetase exist in mammals, one specific for ATP and the other for GTP. The GTP-specific form of pig succinyl-CoA synthetase has been crystallized in the presence of GTP and the structure determined to 2.1 Å resolution. GTP is bound in the ATP-grasp domain, where interactions of the guanine base with a glutamine residue (Gln-20β) and with backbone atoms provide the specificity. The γ-phosphate interacts with the side chain of an arginine residue (Arg-54β) and with backbone amide nitrogen atoms, leading to tight interactions between the γ-phosphate and the protein. This contrasts with the structures of ATP bound to other members of the family of ATP-grasp proteins where the γ-phosphate is exposed, free to react with the other substrate. To test if GDP would interact with GTP-specific succinyl-CoA synthetase in the same way that ADP interacts with other members of the family of ATP-grasp proteins, the structure of GDP bound to GTP-specific succinyl-CoA synthetase was also determined. A comparison of the conformations of GTP and GDP shows that the bases adopt the same position but that changes in conformation of the ribose moieties and the α- and β-phosphates allow the γ-phosphate to interact with the arginine residue and amide nitrogen atoms in GTP, while the β-phosphate interacts with these residues in GDP. The complex of GTP with succinyl-CoA synthetase shows that the enzyme is able to protect GTP from hydrolysis when the active-site histidine residue is not in position to be phosphorylated.