The regulation of the 2-oxoglutarate dehydrogenase complex is central to intramitochondrial energy metabolism. In the present study, the active full-length E1 subunit of the human complex has been expressed and shown to be regulated by Ca2+, adenine nucleotides and NADH, with NADH exerting a major influence on the K0.5 value for Ca2+. We investigated two potential Ca2+-binding sites on E1, which we term site 1 (D114ADLD) and site 2 (E139SDLD). Comparison of sequences from vertebrates with those from Ca2+-insensitive non-vertebrate complexes suggest that site 1 may be the more important. Consistent with this view, a mutated form of E1, D114A, shows a 6-fold decrease in sensitivity for Ca2+, whereas variant ∆site1 (in which the sequence of site 1 is replaced by A114AALA) exhibits an almost complete loss of Ca2+ activation. Variant ∆site2 (in which the sequence is replaced with A139SALA) shows no measurable change in Ca2+ sensitivity. We conclude that site 1, but not site 2, forms part of a regulatory Ca2+-binding site, which is distinct from other previously described Ca2+-binding sites.
Studies on the regulation of the human E1 subunit of the 2-oxoglutarate dehydrogenase complex, including the identification of a novel calcium-binding site
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Craig T. Armstrong, J. L. Ross Anderson, Richard M. Denton; Studies on the regulation of the human E1 subunit of the 2-oxoglutarate dehydrogenase complex, including the identification of a novel calcium-binding site. Biochem J 15 April 2014; 459 (2): 369–381. doi: https://doi.org/10.1042/BJ20131664
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