Nucleic Acids, Protein Synthesis, and Molecular Genetics
Cloning and Characterization of a Dihydrolipoamide Acetyltransferase (E2) Subunit of the Pyruvate Dehydrogenase Complex from Arabidopsis thaliana(∗)

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A cDNA encoding a dihydrolipoamide acetyltransferase (E2) subunit of the pyruvate dehydrogenase complex has been isolated from Arabidopsis thaliana. A cell culture cDNA expression library was screened with a monoclonal antibody (JIM 63) raised against nuclear matrix proteins, and four clones were isolated. One of these was 2175 base pairs in length, and it contained an open reading frame with an amino acid sequence and domain structure with strong similarity to the E2s of other eukaryotic and prokaryotic organisms. The organization and number of functional domains within the Arabidopsis protein are identical to those of the human E2, although the amino acid sequences within these domains are equally similar to those of the yeast and human proteins. The predicted amino acid sequence reveals the presence of a putative amino-terminal leader sequence with characteristics similar to those of other proteins, which are targeted to the plant mitochondrial matrix. The cross-reactivities of plant mitochondrial matrix proteins with JIM 63 and antibodies raised against the E2 and protein X components of eukaryotic pyruvate dehydrogenase complexes are consistent with the clone encoding a mitochondrial form of E2 and not the smaller protein X. The E2 mRNA of 2.2 kilobases was expressed in a range of Arabidopsis and Brassica napus tissues.

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This work was supported in part by the Agricultural and Food Research Council of the United Kingdom via a grant-in-aid to the John Innes Institute. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) Z46230.

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Supported by a John Innes Foundation studentship.