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CHEMBIORAD Working Groups

Sulphur, aromatic and proline residues (WG2)

WG Leader: Prof. Chantal Houeè-Levin; e-mail:

This WG deals with the free radical induced transformation of peptide or protein sequences due to reactions occurring at the level of the targeted amino acid residues Cysteine, Methionine, Proline and aromatics. These residues were envisaged as the most interesting for their involvement in the radical-based functioning of several proteins and enzymes, as well as for their reactivity under radical conditions. Any modification of these residues can lead to chemical mutation and change of biological activity. The activity of this WG is closely related to other radical pathways studied in the Action, such as the transformation of membrane lipids, nucleic acid units and the formation of small radical species.

The groups involved in WG2 are:

  1. Chantal Houée-Levin (WG leader) - University of Paris-Sud, Orsay (France)
  2. Silvia Atrian - Universitat de Barcelona (Spain)
  3. Krzysztof Bobrowski - INCT, Warsaw (Poland)
  4. Anna Croft - University of Wales, Bangor (UK)
  5. Jan Enghild - Aarhus University (Denmark)
  6. Bronislaw Marciniak - Adam Mickiewicz University, Poznan (Poland)
  7. Philippe Renaud - University of Bern (Switzerland)
  8. Andrea Scaloni - CNR, Napoli (Italy)
  9. Troels Skrydstrup - Aarhus University (Denmark)

The main subjects for collaborative research are:

  • Molecular mechanisms of radical-induced transformations including one-electron redox processes and intramolecular electron transfer mechanisms. Biochemical and biological consequences.
  • Production of small radical species during enzyme functioning. Effect on structure and function of model peptides and whole protein sequences with special attention to inflammatory events.
  • Role of reductive stress conditions in the selective modification of methionine residues in protein- liposomes models.
  • Tandem damages involving proteins and nucleic acids.

Tasks will involve the two complimentary aspects of radical biochemistry: the beneficial radical-based mechanisms of biological functions, and the deleterious radical damage caused to biomolecules.

Some details of the WG2 tasks are given below:

Radical functioning:
The aim is to study the involvement of radical species in the activity of enzymes and effect of inhibitors: mechanism of cellular free radical production; spectroscopical detection and trapping of radical intermediates and identification of markers for radical-based enzymatic activity.
  • Investigation of enzymes that exploit radical intermediates, playing essential roles in primary metabolic pathways (cobalamin-dependent enzymes, 2-oxoglutarate dehydrogenase complex, thiol-disulfide oxidoreductase, NADPH oxidase), by experimental and also by quantum mechanical methods.
  • Studies directed to understanding the electron transfer pathways undertaken by proteins and enzymes either intramolecular or in protein assemblies.
  • Development of model compounds and isotopically labelled substrates for the elucidation of reaction mechanisms.
  • Studies focused on identifying transient intermediates in reactions catalysed by radical enzymes.

Radical damaging:
Use of model peptides and intact proteins, combined with proteomic analyses for the identification of radical induced structural changes. Structural and biological evaluation of the modifications.
  • Studies of radical degradation of methionine-containing peptides and proteins (e.g. beta amyloid peptides and Met-enkephalin). Product studies and mechanism of radical degradation. Methionine modification to alpha-aminobutyric acid and influence on structure and activity. Studies in the presence of oxygen, e.g., hydroperoxides formation in peptides and proteins. Influence of the optical isomerism (D, L) in model peptides. Mechanisms of protection of methionine.
  • Specifically modified peptides (e.g., with controlled conformational rigidity by inserting oligoproline bridges and cyclisation) for the study of the generation and fate of radical species.
  • Identification of nitrated protein targets and characterisation of modification sites in AD1 brains.
  • Assays of modified beta-amyloid peptide and Met-enkephalin in vitro and in vivo in collaboration with partners of the Action. The proteomic library will be used in case studies of human pathologies (AD, analgesic activity) in collaboration with medical units.
  • Contribution of peptide bonds in stabilisation of S-centred radical cations: formation of three-electron-bonded intermediates.
  • Models of collagen degradation for product identification and chain cleavage mechanisms. Isolation and structural identification of such collagen fragments, and preparation of antibodies. Follow-up of tissue degradation during radiation therapy in collaboration with biological/medical research units.
  • Involvement of radical pathway in the TAT protein activity and role of the cysteine-rich portion needed for the HIV viral aggression, in collaboration with biological/medical research units.
  • Biochemical characterisation of antioxidant enzyme extracellular superoxide dismutase (ECSOD) and its role during oxidative stress events. These studies will involve collaborators from the medical units.
  • Assays of newly designed superoxide scavengers without production of hydrogen peroxide in collaboration with the biological/medical research units.

Collaboration with other WGs

There will be activities in collaboration with other WGs in particular for the following subjects:
- Use of protein/peptide sequences for studies of the membrane interaction and tandem damages
- Experiments in liposomes for the role of reductive stress conditions in the selective modification of methionine residues in collaboration with WG1;
- Studies of small radical species produced during enzyme functioning and during inflammatory events, and their effect on structure and function of model peptides and whole protein sequences in collaboration with WG4;
- Collaboration with WG3 for tandem damages involving proteins and nucleic acids;
- Collaboration with other WGs to the definition of apoptosis conditions and with medical units for further application of biomarkers in diagnosis;
- Experiment in liposomes for studies of membrane proteins and membrane interaction related to free radical reactions.

1 AD: Alzheimer’s disease.