1jz2
E. COLI (lacZ) BETA-GALACTOSIDASE-TRAPPED 2-F-GALACTOSYL-ENZYME INTERMEDIATE (ORTHORHOMBIC)
|
OverviewOverview
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.
About this StructureAbout this Structure
1JZ2 is a Single protein structure of sequence from Escherichia coli with 2FG, MG, NA, DMS and BTB as ligands. Active as Beta-galactosidase, with EC number 3.2.1.23 Full crystallographic information is available from OCA.
ReferenceReference
A structural view of the action of Escherichia coli (lacZ) beta-galactosidase., Juers DH, Heightman TD, Vasella A, McCarter JD, Mackenzie L, Withers SG, Matthews BW, Biochemistry. 2001 Dec 11;40(49):14781-94. PMID:11732897
Page seeded by OCA on Tue Nov 20 18:42:22 2007