A Structural View of the Action of Escherichia Coli (Lacz) Beta-GalactosidaseJuers, D.H., Heightman, T.D., Vasella, A., McCarter, J.D., Mackenzie, L., Withers, S.G., Matthews, B.W.
(2001) Biochemistry 40: 14781-14794
- PubMed: 11732897
- Primary Citation of Related Structures:
- PubMed Abstract:
- Crystallization of beta-galactosidase from Escherichia coli
Jacobson, R.H.,Matthews, B.W.
(1992) J.Mol.Biol. 223: 1177
- High Resolution Structure of Beta-Galactosidase in a New Crystal Form Reveals Multiple Metal-Binding Sites and Provides a Structural Basis for Alpha-Complementation
Juers, D.H.,Jacobson, R.H.,Wigley, D.,Zhang, X.J.,Huber, R.E.,Tronrud, D.E.,Matthews, B.W.
(2000) Protein Sci. 9: 1685
- Structural Comparisons of Tim Barrel Proteins Suggest Functional and Evolutionary Relationships between Beta-Galactosidase and Other Glycohydrolases
Juers, D.H.,Huber, R.E.,Matthews, B.W.
(1999) Protein Sci. 8: 122
- Three-Dimensional Structure of Beta-Galactosidase from E. Coli
Jacobson, R.H.,Zhang, X.J.,Dubose, R.F.,Matthews, B.W.
(1994) Nature 369: 761
The structures of a series of complexes designed to mimic intermediates along the reaction coordinate for beta-galactosidase are presented. These complexes clarify and enhance previous proposals regarding the catalytic mechanism. The nucleophile, Glu ...
The structures of a series of complexes designed to mimic intermediates along the reaction coordinate for beta-galactosidase are presented. These complexes clarify and enhance previous proposals regarding the catalytic mechanism. The nucleophile, Glu537, is seen to covalently bind to the galactosyl moiety. Of the two potential acids, Mg(2+) and Glu461, the latter is in better position to directly assist in leaving group departure, suggesting that the metal ion acts in a secondary role. A sodium ion plays a part in substrate binding by directly ligating the galactosyl 6-hydroxyl. The proposed reaction coordinate involves the movement of the galactosyl moiety deep into the active site pocket. For those ligands that do bind deeply there is an associated conformational change in which residues within loop 794-804 move up to 10 A closer to the site of binding. In some cases this can be inhibited by the binding of additional ligands. The resulting restricted access to the intermediate helps to explain why allolactose, the natural inducer for the lac operon, is the preferred product of transglycosylation.
Institute of Molecular Biology, Howard Hughes Medical Institute and Department of Physics, University of Oregon, Eugene, Oregon 97403-1229, USA.