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United States Department of Agriculture

Agricultural Research Service

Title: Why Do Plant Mitochondria Have Both Mono and Di-Ipoyl Types of Dihydrolipoyl Acetyltransferase?

Authors
item Broz, A - UNIV OF MISSOURI
item Mooney, B - UNIV OF MISSOURI
item Miernyk, Jan
item Randall, D - UNIV OF MISSOURI

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 3, 2002
Publication Date: N/A

Technical Abstract: The mitochondrial pyruvate dehydrogenase complex (PDC) consists of multiple copies of three enzymes; pyruvate dehydrogenase (E1), dihydrolipoamide acetyltransferase (E2), and dihydrolipoamide dehydrogenase (E3), plus intrinsic kinase and phosphatase regulatory enzymes. The proteins assemble non-covalently into a 8 MDa complex. The core of the eukaryotic PDC is a 60-mer of E2 subunits comprising a pentagonal dodecahedron. There are three types of E2 proteins, characterized by having 1, 2, or 3 lipoyl prosthetic groups. The 3-lipoyl type proteins are apparently restricted to prokaryotes. Mammalian and yeast mitochondria contain the 2-lipoyl type proteins. Results from analyses to date indicate that flowering plant mitochondria all contain the 1-lipoyl type of E2. However, some dicot plants exhibit the 2-lipoyl type of E2 in addition to the 1-lipoyl type. We recently identified three Arabidopsis thaliana mitochondrial PDC E2 genes, a 2-lipoyl type plus two distinct 1-lipoyl types. Both A. thaliana 1-lipoyl cDNAs were cloned and sequenced. Expression of the mRNAs for the three forms of PDC E2 genes was analyzed using RT-PCR. Patterns of expression varied within and between organs. Both 1-lipoyl cDNAs have been cloned and the recombinant proteins will be used in comparative studies with the previously isolated 2-lipoyl E2. In order to verify mitochondrial localization, the cDNAs will also be used for in-vitro import studies. The comparisons of the 1- and 2-lipoyl types of E2 from A. thaliana will contribute to our understanding of the assembly and regulation of mitochondrial PDC, as well as the interactions among components of both the core and overall complex.

Last Modified: 11/28/2014
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