Submitted to: Protein Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2000
Publication Date: 7/1/2000
Citation: MOONEY, B.P., HENZEL, M.T., MIERNYK, J.A., RANDALL, D.D. THE DIHYDROLIPOYL-ACYLTRANSFERASE (BCE2) SUBUNIT OF THE PLANT BRANCHED- CHAIN ALPHA-KETO-ACID DEHYDROGENASE COMPLEX FORMS A 24-MER CORE WITH OCTAGONAL SYMMETRY. PROTEIN SCIENCE. 2000. V. 9(7). P. 1334-1339. Interpretive Summary: Respiration is the use of energy by living cells to do work. Both growth and reproduction are affected by respiration. As a result, respiration must be carefully controlled or wasted energy would decrease crop yields and reduce agricultural productivity. The control of respiration in plant cells is a subject of ongoing study. A protein that is important in the regulation of respiration was isolated from the model plant, Arabidopsis thaliana, and studied. Comparisons were made with the homologous protein from animals and microbes in order to predict characteristics that might be important in control of respiration. A method was developed to produce a biologically active form of the protein in bacteria. The structure of this protein was determined. This information will be important to researchers in their attempts to increase agricultural productivity by altering the control of plant cell respiration, and to other plant scientists who will try to design more efficient crop plants through eithe classical breeding or biotechnology.
Technical Abstract: Little is known about the plant branched-chain alpha-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 other enzymes attach. Mature Arabidopsis thaliiana 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 a S coefficient of 19.4, consitent with the formation of a 24-mer. Negative-staining transmission electron microscopy of the recombinant protein confirmed that BCE2 forms a core with octagonal symmetry. Despite sequence divergence of mammalian and plant BCE2s, clearly there is conservation of structure which is independent of primary sequence.