Component X of mammalian pyruvate dehydrogenase complex: Structural and functional relationship to the lipoate acetyltransferase (E2) component

摘要

>The lipoate acetyltransferase (E2, M _r 70 000) and protein X (M _r 51 000) subunits of the bovine pyruvate dehydrogenase multienzyme complex (PDC) core assembly are antigenically distinct polypeptides. However comparison of the N-terminal amino acid sequence of the E2 and X polypeptides reveals significant homology between the two components. Selective tryptic release of the 14C-labelled acetylated lipoyl domains of E2 and protein X from native PDC generates stable, radiolabelled 34 and 15 kDa fragments, respectively. Thus, in contrast to E2 which contains two tandemly-arranged lipoyl domains, protein X appears to contain only a single lipoyl domain located at its N-terminus.