1.9-A structures of ternary complexes of citrate synthase with D- and L-malate: mechanistic implications.Karpusas, M., Holland, D., Remington, S.J.
(1991) Biochemistry 30: 6024-6031
- PubMed: 2043640
- Primary Citation of Related Structures:
- PubMed Abstract:
- Crystal Structure Analysis and Molecular Model of a Complex of Citrate Synthase with Oxaloacetate and S-Acetonyl-Coenzymea
Wiegand, G.,Remington, S.,Deisenhofer, J.,Huber, R.
(1984) J.Mol.Biol. 174: 205
- Primary Structure of Porcine Heart Citrate Synthase
Bloxham, D.P.,Parmelee, D.C.,Kumar, S.,Wade, R.D.,Ericsson, L.H.,Neurath, H.,Walsh, K.A.,Titani, K.
(1981) Proc.Natl.Acad.Sci.USA 78: 5381
- Crystal Structure Analysis of the Tetragonal Crystal Form and Preliminary Molecular Model of Pig-Heart Citrate Synthase
Wiegand, G.,Kukla, D.,Scholze, H.,Jones, T.A.,Huber, R.
(1979) Eur.J.Biochem. 93: 41
- Crystallographic Refinement and Atomic Models of Two Different Forms of Citrate Synthase at 2.7 And 1.7 Angstroms Resolution
Remington, S.,Wiegand, G.,Huber, R.
(1982) J.Mol.Biol. 158: 111
The structures of four isomorphous crystals of ternary complexes of chicken heart citrate synthase with D- or L-malate and acetyl coenzyme A or carboxymethyl coenzyme A have been determined by X-ray crystallography and fully refined at 1.9-A resoluti ...
The structures of four isomorphous crystals of ternary complexes of chicken heart citrate synthase with D- or L-malate and acetyl coenzyme A or carboxymethyl coenzyme A have been determined by X-ray crystallography and fully refined at 1.9-A resolution. The structures show that both L-malate and D-malate bind in a very similar way in the presence of acetylCoA and that the enzyme conformation is "closed". Hydrogen bond geometry is suggested to account for the difference in binding constants of the two stereoisomers. The structures suggest that steric hindrance can account for the observation that proton exchange of acetyl coenzyme A with solvent is catalyzed by citrate synthase in the presence of L-malate but not D-malate. The ternary complexes with malate reveal the mode of binding of the substrate acetylCoA in the ground state. The carbonyl oxygen of the acetyl group is hydrogen bonded to a water molecule and to histidine 274, allowing unambiguous identification of the orientation of this group. The structures support the hypothesis that carboxymethyl coenzyme A is a transition-state analogue for the enolization step of the reaction (Bayer et al., 1981) and additionally support proposed mechanisms for the condensation reaction (Karpusas et al., 1990; Alter et al., 1990).
Institute of Molecular Biology, University of Oregon, Eugene 97403.