MOBILITY IN PYRUVATE-DEHYDROGENASE COMPLEXES WITH MULTIPLE LIPOLYL DOMAINS

High-field NMR studies were carried out with genetically-reconstructed pyruvate dehydrogenase (PDH) complexes of Escherichia coli containing from zero to nine lipoyl domains per lipoate acetyltransferase (E2p) subunit. The only significant differences between the NMR spectra were the increasing intensities of the signals derived from the lipoyl domains and their associated linkers, and the much enhanced signal from the E3-binding domain and its linker in complexes that are devoid of lipoyl domains. The results suggest an explanation for the presence of three lipoyl domains per E2p subunit in the wild-type PDH complex, based on its greater inherent mobility, and potentially more efficient active-site coupling, than any of the other complexes.