2fpg: Difference between revisions

[[Image:2fpg.gif|left|200px]]<br /><applet load="2fpg" size="350" color="white" frame="true" align="right" spinBox="true"  

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 A resolution. GTP is bound in the ATP-grasp domain, where interactions of the guanine base with a glutamine residue (Gln-20beta) and with backbone atoms provide the specificity. The gamma-phosphate interacts with the side chain of an arginine residue (Arg-54beta) and with backbone amide nitrogen atoms, leading to tight interactions between the gamma-phosphate and the protein. This contrasts with the structures of ATP bound to other members of the family of ATP-grasp proteins where the gamma-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 alpha- and beta-phosphates allow the gamma-phosphate to interact with the arginine residue and amide nitrogen atoms in GTP, while the beta-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.

2FPG is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Sus_scrofa Sus scrofa] with <scene name='pdbligand=K:'>K</scene>, <scene name='pdbligand=PO4:'>PO4</scene> and <scene name='pdbligand=GDP:'>GDP</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Succinate--CoA_ligase_(GDP-forming) Succinate--CoA ligase (GDP-forming)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=6.2.1.4 6.2.1.4] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2FPG OCA].  

[[Category: Fraser, M E.]]

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