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A structural model for human dihydrolipoamide dehydrogenase
Author(s) -
Jentoft Joyce E.,
Shoham Menachem,
Hurst Darren,
Patel Mulchand S.
Publication year - 1992
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.340140110
Subject(s) - dihydrolipoamide dehydrogenase , cofactor , active site , protein tertiary structure , mutagenesis , nad+ kinase , biochemistry , stereochemistry , acetyltransferase , chemistry , dehydrogenase , biology , enzyme , mutation , acetylation , gene
Abstract The hypothesis that dihydrolipoamide dehydrogenases (E 3 s) have tertiary structures very similar to that of human glutathione reductase (GR) was tested in detail by three separate criteria: (1) by analyzing each putative secondary structural element for conservation of appropriate polar/nonpolar regions, (2) by detailed comparison of putative active site residues in E 3 s with their authentic counterparts in human GR, and (3) by comparison of residues at the putative dimeric interface of the E 3 s with the authentic residues in GR. All three criteria are satisfied in a convincing way for the 7 E 3 s that were considered, supporting the conclusion that the structural scaffolding and the overall tertiary structure (which determines the location of functional sites and residues) are remarkably similar for the E 3 s and for GR. These analyses together with the crystal structures of human erythrocyte GR formed the basis for construction of a molecular model for human E 3 . The cofactor FAD and the substrakes NAD and lipoic acid were also included in the model. Unexpectedly, the surface residues in the cleft that holds the lipoamide were found to be highly charged and predominantly acidic, allowing us to predict that the region around the lipoamide in the sub‐unit should be basic in nature. The molecular model can be tested by site‐directed mutagenesis of residues predicted to be in the dihydrolipoamide acetyltransferase subunit binding cleft. © 1992 Wiley‐Liss, Inc.