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The dihydrolipoyl acyltransferase (BCE2) subunit of the plant branched-chain α-ketoacid dehydrogenase complex forms a 24-mer core with octagonal symmetry

Published online by Cambridge University Press:  01 July 2000

BRIAN P. MOONEY
Affiliation:
Biochemistry Department, University of Missouri, Columbia, Missouri 65211
MICHAEL T. HENZL
Affiliation:
Biochemistry Department, University of Missouri, Columbia, Missouri 65211
JAN A. MIERNYK
Affiliation:
Biochemistry Department, University of Missouri, Columbia, Missouri 65211 Plant Genetics Research Unit, USDA, ARS, Columbia, Missouri 65211
DOUGLAS D. RANDALL
Affiliation:
Biochemistry Department, University of Missouri, Columbia, Missouri 65211
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Abstract

Little is known of the plant branched-chain α-ketoacid dehydrogenase complex. We have undertaken a detailed study of the structure of the dihydrolipoyl acyltransferase (BCE2) subunit that forms the core of the complex, to which two other enzymes attach. Mature Arabidopsis thaliana BCE2 was expressed in Escherichia coli. The soluble recombinant protein was purified using a Superose 6 size-exclusion column to >90% homogeneity and was catalytically active. The recombinant protein formed a stable complex with a native molecular mass of 0.95 MDa and an S coefficient of 19.4, consistent with formation of a 24-mer. Negative-staining transmission electron microscopy of the recombinant protein confirmed that BCE2 forms a core with octagonal symmetry. Despite divergence of mammalian and plant BCE2s, there is clearly conservation of structure that is independent of primary sequence.

Type
Research Article
Copyright
2000 The Protein Society

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