Why are the 2-oxoacid dehydrogenase complexes so large? Generation of an active trimeric complex

DOI: 10.1042/BJ20140359
PMID: 25088564

Authors: Nia Marrott (University of Bath) , Jacqueline J. T. Marshall (Cancer Research UK) , Dmitri I. Svergun (EMBL) , Susan J. Crennell (University of Bath) , David W. Hough (University of Bath) , Jean M. H. Van Den Elsen (University of Bath) , Michael J. Danson (University of Bath)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical Journal , VOL 463 , PAGES 405-412

State: Published (Approved)
Published: May 2014
Diamond Proposal Number(s): 7131

Abstract: The four-component polypeptides of the 2-oxoacid dehydrogenase complex from the thermophilic archaeon Thermoplasma acidophilum assemble to give an active multienzyme complex possessing activity with the branched-chain 2-oxoacids derived from leucine, isoleucine and valine, and with pyruvate. The dihydrolipoyl acyl-transferase (E2) core of the complex is composed of identical trimer-forming units that assemble into a novel 42-mer structure comprising octahedral and icosahedral geometric aspects. From our previously determined structure of this catalytic core, the inter-trimer interactions involve a tyrosine residue near the C-terminus secured in a hydrophobic pocket of an adjacent trimer like a ball-and-socket joint. In the present study, we have deleted the five C-terminal amino acids of the E2 polypeptide (IIYEI) and shown by equilibrium centrifugation that it now only assembles into a trimeric enzyme. This was confirmed by SAXS analysis, although this technique showed the presence of approximately 20% hexamers. The crystal structure of the trimeric truncated E2 core has been determined and shown to be virtually identical with the ones observed in the 42-mer, demonstrating that removal of the C-terminal anchor does not significantly affect the individual monomer or trimer structures. The truncated E2 is still able to bind both 2-oxoacid decarboxylase (E1) and dihydrolipoamide dehydrogenase (E3) components to give an active complex with catalytic activity similar to the native multienzyme complex. This is the first report of an active mini-complex for this enzyme, and raises the question of why all 2-oxoacid dehydrogenase complexes assemble into such large structures.

Journal Keywords: archaea; macromolecular assembly; multienzyme complex; 2-oxoacid dehydrogenase; thermophile; X-ray crystallography

Diamond Keywords: Archaea; Enzymes

Subject Areas: Biology and Bio-materials


Instruments: I04-Macromolecular Crystallography

Other Facilities: DESY-EMBL beamlines

Added On: 25/09/2014 15:50

Discipline Tags:

Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX)