Post-translational modification in the archaea: structural characterization of multi-enzyme complex lipoylation

Biochem J. 2013 Jan 15;449(2):415-25. doi: 10.1042/BJ20121150.


Lipoylation, the covalent attachment of lipoic acid to 2-oxoacid dehydrogenase multi-enzyme complexes, is essential for metabolism in aerobic bacteria and eukarya. In Escherichia coli, lipoylation is catalysed by LplA (lipoate protein ligase) or by LipA (lipoic acid synthetase) and LipB [lipoyl(octanoyl) transferase] combined. Whereas bacterial and eukaryotic LplAs comprise a single two-domain protein, archaeal LplA function typically involves two proteins, LplA-N and LplA-C. In the thermophilic archaeon Thermoplasma acidophilum, LplA-N and LplA-C are encoded by overlapping genes in inverted orientation (lpla-c is upstream of lpla-n). The T. acidophilum LplA-N structure is known, but the LplA-C structure is unknown and LplA-C's role in lipoylation is unclear. In the present study, we have determined the structures of the substrate-free LplA-N-LplA-C complex and E2lipD (dihydrolipoyl acyltransferase lipoyl domain) that is lipoylated by LplA-N-LplA-C, and carried out biochemical analyses of this archaeal lipoylation system. Our data reveal the following: (i) LplA-C is disordered but folds upon association with LplA-N; (ii) LplA-C induces a conformational change in LplA-N involving substantial shortening of a loop that could repress catalytic activity of isolated LplA-N; (iii) the adenylate-binding region of LplA-N-LplA-C includes two helices rather than the purely loop structure of varying order observed in other LplA structures; (iv) LplAN-LplA-C and E2lipD do not interact in the absence of substrate; (v) LplA-N-LplA-C undergoes a conformational change (the details of which are currently undetermined) during lipoylation; and (vi) LplA-N-LplA-C can utilize octanoic acid as well as lipoic acid as substrate. The elucidated functional inter-dependence of LplA-N and LplA-C is consistent with their evolutionary co-retention in archaeal genomes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Monophosphate / chemistry
  • Adenosine Monophosphate / metabolism
  • Archaeal Proteins / chemistry
  • Archaeal Proteins / genetics
  • Archaeal Proteins / metabolism*
  • Binding Sites
  • Crystallography, X-Ray
  • Dihydrolipoyllysine-Residue Acetyltransferase / chemistry
  • Dihydrolipoyllysine-Residue Acetyltransferase / genetics
  • Dihydrolipoyllysine-Residue Acetyltransferase / metabolism
  • Isoenzymes / chemistry
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Lipoylation
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Multiprotein Complexes / chemistry
  • Multiprotein Complexes / metabolism
  • Peptide Synthases / chemistry
  • Peptide Synthases / genetics
  • Peptide Synthases / metabolism*
  • Protein Binding
  • Protein Conformation
  • Protein Processing, Post-Translational*
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Substrate Specificity
  • Thermoplasma / enzymology*
  • Thioctic Acid / chemistry
  • Thioctic Acid / metabolism


  • Archaeal Proteins
  • Isoenzymes
  • Multiprotein Complexes
  • Recombinant Proteins
  • Adenosine Monophosphate
  • Thioctic Acid
  • Dihydrolipoyllysine-Residue Acetyltransferase
  • Peptide Synthases
  • lipoate-protein ligase