Primary Structure and Post-translational Modification of Ferredoxin-NADP Reductase from Chlamydomonas reinhardtii

The flavoprotein ferredoxin-NADP reductase (FNR) was isolated from the unicellular green alga, Chlamydomonas reinhardtii. FNR is a monomeric protein containing one FAD and exhibiting ferredoxin-dependent cytochrome c reduction activity. Its complete primary structure was investigated by sequencing overlapping peptides generated by cleavage with trypsin and SV8 protease and confirmed by partial (80%) nucleotidic sequence. C. reinhardtii FNR contains 320 residues, coresponding to a calculated mass of 35,685 and 36,470 including FAD, in agreement with the values measured by laser desorption mass spectrometry. The combination of both amino acid and nucleotidic sequencing, in association with mass spectrometry of peptides, allowed the identification of two Nϵ-trimethyllysines at positions 83 and 89 and one Nϵ-dimethyllysine at position 135. Comparison of the primary structure of C. reinhardtii FNR with the known sequences shows 41-46% identity.