Photosynthesis Research 79: 357–367, 2004. © 2004 Kluwer Academic Publishers. Printed in the Netherlands. 357 Review NMR of redox proteins of plants, yeasts and photosynthetic bacteria Xavier Trivelli, Sandrine Bouillac, Pascale Tsan, Isabelle Krimm & Jean-Marc Lancelin ∗ Laboratoire de RMN Biomol´ eculaire associ´ e au CNRS, Universit´ e Claude Bernard – Lyon 1, Domaine Scientifique de La Doua, Ecole Sup´ erieure de Chimie Physique Electronique de Lyon, 69622, Villeurbanne, France; ∗ Author for correspondence (e-mail: lancelin@hikari.cpe.fr; fax: +33-472-431395) Received 25 June 2003; accepted in revised form 18 August 2003 Key words: electron transfer, NMR, redox proteins, redox signaling Abstract NMR spectroscopy has evolved dramatically over the past 15 years, establishing a new, reliable methodology for studying biomacromolecules at atomic resolution. The three-dimensional structure and dynamics of a biomolecule or a biomolecular complex is only one of the main types of information available using NMR. The spectral assign- ment to the specific nuclei of a biostructure is a very precise reflection of their electronic environment. Any change in this environment due to a structural change, the binding of a ligand or the redox state of a redox cofactor, will be very sensitively reported by changes in the different NMR parameters. The capabilities of the NMR method are currently expanding dramatically and it is turning into a powerful means to study biosystems dynamically in exchange between different conformations, exchanging ligands, transient complexes, or the activation/inhibition of regulated enzymes. We review here several NMR studies that have appeared during the past 5 or 6 years in the field of redox proteins of plants, yeasts and photosynthetic bacteria. These new results illustrate the recent bio- molecular NMR evolution and provide new physiological models for understanding the different types of electron transfer, including glutaredoxins, thioredoxins and their dependent enzymes, the ferredoxin-NADP oxidoreductase complex, flavodoxins, the plastocyanin–cytochrome f complex, and cytochromes c. Abbreviations: FD – ferredoxin; FDX – flavodoxin; FNR – ferredoxin NADP oxidoreductase; GRX – glutaredoxin; HSQC – heteronuclear single quantum coherence spectroscopy; MDH – malate dehydrogenase; PS I – Photosystem I; RDC – residual dipolar couplings; RNR – ribonucleotide reductase Introduction Redox proteins of plants, yeasts and photosynthetic bacteria have particularly been studied using NMR spectroscopy. The main recent interests are particu- larly studies of their molecular dynamics, compar- ative dynamics of reduced and oxidized states, and the study of protein–protein interactions during elec- tron transfer. NMR spectroscopy is currently the most rapidly expanding experimental method for studying the structure-activity relationships of biomacromole- cules. The recent Nobel Prize for Chemistry (2002) awarded to Professor Kurt Wüthrich is significant testimony to this expansion (Wüthrich 2003). Very early on, about 20 years ago, the different NMR methodologies showed great potential for providing a new, fundamental method for studying biological macromolecules, besides X-ray crystallography. Sev- eral steps needed to be taken, though. First, the NMR signals of the very complex spectra of biopolymers had to be individually and unambiguously assigned to specific nuclei of the structure (Wüthrich 1986). In a second step, the magnitude of specific NMR effects were translated to structural restraints, which were kept approximate to take account of the structural dy- namics in solution. The entire NMR restraint set was demonstrated to support reliable structural models in aqueous solution (Wagner et al. 1987).