2nu6
C123aA Mutant of E. coli Succinyl-CoA Synthetase
Structural highlights
FunctionSUCD_ECOLI During aerobic metabolism it functions in the citric acid cycle, coupling the hydrolysis of succinyl-CoA to the synthesis of ATP and thus represents an important site of substrate-level phosphorylation. It can also function in the other direction for anabolic purposes, and this may be particularly important for providing succinyl-CoA during anaerobic growth when the oxidative route from 2-oxoglutarate is severely repressed. The alpha-subunit binds CoA, as well as ATP and catalyzes phosphoryl transfer to one of its histidine residues. The complete active site is probably located in the region of alpha-beta contact. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedSuccinyl-CoA synthetase has a highly conserved cysteine residue, Cys123alpha in the Escherichia coli enzyme, that is located near the CoA-binding site and the active-site histidine residue. To test whether the succinyl moiety of succinyl-CoA is transferred to the thiol of Cys123alpha as part of the catalytic mechanism, this residue was mutated to alanine, serine, threonine and valine. Each mutant protein was catalytically active, although less active than the wild type. This proved that the specific formation of a thioester bond with Cys123alpha is not part of the catalytic mechanism. To understand why the mutations affected catalysis, the crystal structures of the four mutant proteins were determined. The alanine mutant showed no structural changes yet had reduced activity, suggesting that the size of the cysteine is important for optimal activity. These results explain why this cysteine residue is conserved in the sequences of succinyl-CoA synthetases from different sources. Participation of Cys123alpha of Escherichia coli succinyl-CoA synthetase in catalysis.,Hidber E, Brownie ER, Hayakawa K, Fraser ME Acta Crystallogr D Biol Crystallogr. 2007 Aug;63(Pt 8):876-84. Epub 2007, Jul 17. PMID:17642514[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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