Understanding of the 2-oxoglutarate dehydrogenase and 2-oxoadipate dehydrogenase assembly with the E2o core relevant to a hybrid complex formation

The 2-oxoglutarate (OG) dehydrogenase complex (OGDHc) is a key enzyme in the tricarboxylic acid cycle (TCA) and comprises multiple copies of three components: 2-oxoglutarate dehydrogenase (hE1o), dihydrolipoamide succinyltransferase (hE2o), and dihydrolipoamide dehydrogenase (hE3). The OGDHc is one of the major regulators of mitochondrial metabolism through NADH and reactive oxygen species levels and impacts cell metabolic and cell signaling pathways through the coupling of OG metabolism to gene transcription, related to tumor cell proliferation and aging. The reduced OGDHc activity is linked to a number of neurodegenerative diseases. Evidence was obtained for the formation of a hybrid 2-oxo acid dehydrogenase complex between the OGDHc and its homologue 2-oxoadipate (OA) dehydrogenase (hE1a) in the L-lysine metabolic pathway, suggesting a potential cross-talk between the two distinct metabolic pathways. These findings raised fundamental questions about assembly of hE1a and hE1o to the hE2o core. Due to the lack of an atomic structure of the OGDHc from any sources, and of knowledge about exact distribution of components around the E2 core, hydrogen/deuterium exchange (HDX-MS) and chemical cross-linking mass spectrometry (CL-MS) have been carried out in binary hE1o-hE2o, hE1a-hE2o, hE1o-hE3 and hE2o-hE3 sub-complexes followed by structural modeling. Here we report findings that revealed some similarities in the assembly of hE1o and hE1a to the hE2o core. At the same time, three regions of the hE2o core comprising residues 191-208, 273-288, and 370-386 revealed a different binding mode to hE1o and hE1a, suggesting that hE2o can differentiate between these two proteins that may have physiological consequences. ### Competing Interest Statement The authors have declared no competing interest. * OGDHc : 2-oxoglutarate dehydrogenase complex h : human OADHc : 2-oxoadipate dehydrogenase complex E1o : 2-oxoglutarate dehydrogenase E1a : 2-oxoadipate dehydrogenase E2o : dihydrolipoamide succinyltransferase E3 : dihydrolipoamide dehydrogenase LDo : lipoyl domain CDo : E2o catalytic domain PTMs : post-translational modifications TCA cycle : tricarboxylic acid cycle ThDP : thiamin diphosphate DHTKD1 : gene encoding 2-oxoadipate dehydrogenase HDX-MS : hydrogen-deuterium exchange mass spectrometry CL-MS : chemical cross-linking mass spectrometry FT-MS : Fourier transform mass spectrometry cryo-EM : cryogenic electron microscopy CDI : 1,1’-carbonyldiimidazole cross-linker DSBU or BuUrBu : disuccinimidyl dibutyric urea PDB : Protein Data Bank.