PARENT SESSION
Posters P2B Light, redox and metabolic regulation: Light Reactions. Abstracts (444-478)

Ferredoxin NADP⁺ oxidoreductase (FNR) in different domains of the thylakoid membrane. Marjaana Suorsa^*,1, Virpi Paakkarinen¹, Natalia Battchikova¹, Ammar Saleem¹, Ravi Danielsson², Eva-Mari Aro¹, ¹ Department of Biology, Plant Physiology and Molecular Biology, University of Turku, Turku, Finland² Biochemistry, Chemical Center, Lund University, Lund, Sweden

ABSTRACT- Ferredoxin NADP+ oxidoreductase (FNR) is a nuclear-encoded protein in higher plant chloroplasts. FNR catalyses the reduction of ferredoxin, thus forming the last electron transfer step in linear electron flow. FNR is also involved in cyclic electron transfer around PSI. We have studied the location of FNR in higher plant thylakoid membranes. In thylakoids isolated from dark- or low light adapted leaves, FNR was found to be present almost exclusively in stroma-exposed thylakoids, thus indicating a possible connection with Photosystem I. When thylakoid membrane protein complexes were separated by blue-native gel electrophoresis, FNR was found to be present in two complexes and as a free protein. The products of two genes encoding FNR (At5g66190) and FNR-like protein (At1g20020) could be detected in the same complex. FNR also showed post-translational modifications and a possible role of FNR phosphorylation in cyclic and linear electron transfer will be discussed.

KEY WORDS: FNR, Ferredoxin NADP+ oxidoreductase, blue-native gel electrophoresis, thylakoid membrane fractions