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Localization of lipoyl-bearing domains in the alpha-ketoglutarate dehydrogenase multienzyme complex. 1984

T Wagenknecht, and J Frank

The alpha-ketoglutarate dehydrogenase complex from Escherichia coli consists of a core component, dihydrolipoyl transsuccinylase (E2), to which are noncovalently bound 12 polypeptide chains each of alpha-ketoglutarate dehydrogenase and dihydrolipoyl dehydrogenase. E2 exists as a cube-shaped complex comprising 24 identical chains and may be resolved from the other two enzyme components. Limited digestion of E2 with trypsin quantitatively removes domains containing the lipoic acid cofactor while leaving the quaternary structure of the complex intact. Averages of native and trypsin-modified E2 were computed from images of single molecules obtained from electron micrographs of negatively stained specimens. The two averages were very similar and were in general agreement with a model determined previously by X-ray crystallography. However, detailed analysis of the difference image, obtained by subtracting the average of the trypsin-treated E2 from the native E2, showed extra stain-excluding regions along the edges of the native molecule which we interpret as representing the lipoyl-bearing domains. Micrographs of mixtures of native and modified E2 were also analyzed in order to rule out staining or electron-optical artifacts as accounting for the results. On the basis of these results along with other available structural information, we propose that one function of the lipoyl domains is to permit interactions between distantly separated lipoyl moieties in the E2 complex; this proposal also agrees with recent results of modeling studies of biochemical data [Hackert, M.L., Oliver, R.M., & Reed, L.J. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 2226-2230].

UI MeSH Term Description Entries
D007655 Ketoglutarate Dehydrogenase Complex 2-Keto-4-Hydroxyglutarate Dehydrogenase,2-Oxoglutarate Dehydrogenase,2-Oxoglutarate Dehydrogenase Complex,Oxoglutarate Dehydrogenase,alpha-Ketoglutarate Dehydrogenase,alpha-Ketoglutarate Dehydrogenase Complex,2 Keto 4 Hydroxyglutarate Dehydrogenase,2 Oxoglutarate Dehydrogenase,2 Oxoglutarate Dehydrogenase Complex,Complex, 2-Oxoglutarate Dehydrogenase,Complex, Ketoglutarate Dehydrogenase,Complex, alpha-Ketoglutarate Dehydrogenase,Dehydrogenase Complex, 2-Oxoglutarate,Dehydrogenase Complex, Ketoglutarate,Dehydrogenase Complex, alpha-Ketoglutarate,Dehydrogenase, 2-Keto-4-Hydroxyglutarate,Dehydrogenase, 2-Oxoglutarate,Dehydrogenase, Oxoglutarate,Dehydrogenase, alpha-Ketoglutarate,alpha Ketoglutarate Dehydrogenase,alpha Ketoglutarate Dehydrogenase Complex
D007658 Ketone Oxidoreductases Oxidoreductases that are specific for KETONES. Oxidoreductases, Ketone
D008854 Microscopy, Electron Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen. Electron Microscopy
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D011487 Protein Conformation The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain). Conformation, Protein,Conformations, Protein,Protein Conformations
D004926 Escherichia coli A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc. Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D000217 Acyltransferases Enzymes from the transferase class that catalyze the transfer of acyl groups from donor to acceptor, forming either esters or amides. (From Enzyme Nomenclature 1992) EC 2.3. Acyltransferase
D014357 Trypsin A serine endopeptidase that is formed from TRYPSINOGEN in the pancreas. It is converted into its active form by ENTEROPEPTIDASE in the small intestine. It catalyzes hydrolysis of the carboxyl group of either arginine or lysine. EC 3.4.21.4. Tripcellim,Trypure,beta-Trypsin,beta Trypsin

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