Self-assembly and catalytic activity of the pyruvate dehydrogenase multienzyme complex of Escherichia coli

Rapid intramolecular coupling of active sites in the pyruvate dehydrogenase complex of Escherichia coli : Mechanism for rate enhancement in a multimeric structure

“…We therefore proposed that the lipoyllysine swinging arms can participate in two types of subunit interactions: each El dimer can interact directly with the lipoic acid residues of a small number of E2 chains, followed by the transfer of acetyl groups between the lipoic acid residues of neighboring E2 chains in the complex. We referred to these internal reactions as "transacetylations" (6). This work has been confirmed by Collins and Reed (8).…”

“…The mutant organism was kindly provided by H. L. Kornberg. From the native enzyme, four partly reassembled pyruvate dehydrogenase complexes (R1-R4), varying only in their El content, were prepared as described by Bates et al (6). The ratios of the polypeptide chains in these complexes were determined by the radioamidination method of Bates et al (11).…”

Conformational mobility of polypeptide chains in the 2‐oxo acid dehydrogenase complexes from ox heart revealed by proton NMR spectroscopy

“…coli (H. W. Duckworth, R. Jaenicke, R. N. P., G. C. K. R., unpublished). It is a general property of the 2-oxo acid dehydrogenase complexes, and is most likely to be concerned with the unusual systems of the active site coupling possessed by these multienzyme complexes [15][16][17][21][22][23].…”

“…An extraordinary degree of conformational mobility of large segments of the E2 chains encompassing the lipoyl-lysine residues was demonstrated by proton NMR spectroscopy of the E. coli complex [ 14]. It is likely that this mobility greatly extends the working radius of a swinging arm and is intimately connected with the novel system of active site coupling possessed by this enzyme [15][16][17]. We show here by means of proton NMR spectroscopy that Abbreviations: NMR, nuclear magnetic resonance; SDS, sodium dodecyl sulphate;M r, relative molecular mass conformational mobility of this unusual kind is also a property of the pyruvate and 2-oxoglutarate dehydrogenase complexes of ox heart.…”

Pyruvate dehydrogenase multienzyme complex of Escherichia coli

“…There is a continuing controversy over the stoicheiometry of polypeptide chains in the native complex. Direct quantitation of the polypeptides separated by SDS-polyacrylamide gel electrophoresis indicates stoicheiometries of -1.3: 1: 1 (El :E2:E3) in complex as normally isolated [S-7] with an upper limit of 2: 1: 1 [8,9]. On the other hand, calculations by an indirect method, from the Mr of the complex and of the E2 core, gave a polypeptide stoicheiometry of 1: 1 :OS [ 10,111. Inherent in this discrepancy is a disagreement over the M, of the E2 polypeptide.…”