Component X of mammalian pyruvate dehydrogenase complex: structural and functional relationship to the lipoate acetyltransferase (E2) component |
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Authors: | J Neagle O De Marcucci B Dunbar J G Lindsay |
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Institution: | Department of Biochemistry, University of Glasgow, Scotland. |
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Abstract: | The lipoate acetyltransferase (E2, Mr 70,000) and protein X (Mr 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. |
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