ABSTRACT
Introduction...................................................................................................... 217 Properties and Structure of E. coli Lipoate-Protein Ligase A......................... 221 Properties of E. coli LplA............................................................................ 221 Overall Structure of E. coli LplA ................................................................ 222 Lipoic Acid-Binding Site............................................................................. 224
Structure of T. acidophilum Lipoate-Protein Ligase A ................................... 226 Overall Fold of the T. acidophilum LplA Molecule ................................... 226 Substrate-Binding Site ................................................................................. 227
Predicted Catalytic Mechanism of LplA ......................................................... 228 References ........................................................................................................ 231
R-(þ)-lipoic acid is a disulfide-containing cofactor of the pyruvate, a-ketoglutarate, and branched chain a-ketoacid dehydrogenase complexes and the glycine cleavage system. Lipoic acid is covalently bound to a specific lysine residue of the E2 component of the a-ketoacid dehydrogenase complexes and of H-protein of the glycine cleavage system via an amide linkage between the carboxyl group of lipoic acid and the e-amino group of the lysine residue of the lipoate-dependent proteins. The lipoyllysine arm plays a pivotal role in the reaction sequence, shuttling the reaction intermediate and the reducing equivalents between the active sites of the components of the complex (Fujiwara et al., 1992; Perham, 2000).
