 |
PDBsum entry 1xg4
|
|
|
|
References listed in PDB file
|
 |
|
Key reference
|
|
|
Title
|
|
Crystal structures of 2-Methylisocitrate lyase in complex with product and with isocitrate inhibitor provide insight into lyase substrate specificity, Catalysis and evolution.
|
|
|
Authors
|
|
S.Liu,
Z.Lu,
Y.Han,
E.Melamud,
D.Dunaway-Mariano,
O.Herzberg.
|
|
|
Ref.
|
|
Biochemistry, 2005,
44,
2949-2962.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
Two crystal structures of the C123S mutant of 2-methylisocitrate lyase have been
determined, one with the bound reaction products, Mg(2+)-pyruvate and succinate,
and the second with a bound Mg(2+)-(2R,3S)-isocitrate inhibitor. Comparison with
the structure of the wild-type enzyme in the unbound state reveals that the
enzyme undergoes a conformational transition that sequesters the ligand from
solvent, as previously observed for two other enzyme superfamily members,
isocitrate lyase and phosphoenolpyruvate mutase. The binding modes reveal the
determinants of substrate specificity and stereoselectivity, and the stringent
specificity is verified in solution using various potential substrates. A model
of bound 2-methylisocitrate has been developed based on the experimentally
determined structures. We propose a catalytic mechanism involving an
alpha-carboxy-carbanion intermediate/transition state, which is consistent with
previous stereochemical experiments showing inversion of configuration at the
C(3) of 2-methylisocitrate. Structure-based sequence analysis and phylogenic
tree construction reveal determinants of substrate specificity, highlight nodes
of divergence of families, and predict enzyme families with new functions.
|
|
|
|
|
|
|
