The novel component Kgd4 recruits the E3 subunit to the mitochondrial α-ketoglutarate dehydrogenase.
Bottom Line: Biochemical analyses demonstrate that this protein plays an evolutionarily conserved role in the organization of mitochondrial α-KGDH complexes of fungi and animals.By binding to both the E1-E2 core and the E3 subunit, Kgd4 acts as a molecular adaptor that is necessary to a form a stable α-KGDH enzyme complex.Our work thus reveals a novel subunit of a key citric acid-cycle enzyme and shows how this large complex is organized.
Affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.Show MeSH
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Mentions: To test this, we purified complexes of Kgd4ΔN and found that Kgd1 and Kgd2 but not Lpd1 could be copurified with this protein (Figure 7C). This demonstrates that the C-terminal domain of Kgd4 directly interacts with the assembled Kgd1-Kgd2 core because a direct interaction of Kgd4 with Kgd2 can be ruled out according to previous experiments (Figure 5A). Taken together, these data establish that Kgd4 contains two functionally separable domains. While the C-terminal domain is required to establish interactions with the Kgd1-Kgd2 core, the N-terminal domain binds to the E3 subunit Lpd1 (Figure 8A). This architecture likely enables Kgd4 to act as a molecular adaptor between the E3 subunit and the core of KGDH.
Affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.