Molecular adapter that is necessary to form a stable 2- oxoglutarate dehydrogenase enzyme complex (OGDHC). Enables the specific recruitment of E3 subunit to E2 subunit in the 2-oxoglutarate dehydrogenase complex (OGDHC). . This is the function of Ensembl gene identifier ENSG00000134056 (KGD4, alpha-ketoglutarate dehydrogenase subunit 4).