Required for anchoring dihydrolipoamide dehydrogenase (E3) to the dihydrolipoamide transacetylase (E2) core of the pyruvate dehydrogenase complexes of eukaryotes. This specific binding is essential for a functional PDH complex. Eukaryotic pyruvate dehydrogenase (PDH) complexes are organized as a core consisting of the oligomeric dihydrolipoamide acetyl-transferase (E2), around which are arranged multiple copies of pyruvate dehydrogenase (E1), dihydrolipoamide dehydrogenase (E3) and protein X (E3BP) bound by non-covalent bonds. Present with 414 molecules/cell in log phase SD medium. Belongs to the 2-oxoacid dehydrogenase family.