Interaction of ferredoxin-NADP+ reductase with phycobiliproteins in the cyanobacterium Anabaena PCC 7119

A complex between ferredoxin-NADP+ reductase (EC 1.18.1.2.) and phycobiliproteins has been isolated from Anabaena PCC 7119. Two proteins of 18 and 12.5 kDa bound to FNR have been sequenced at the amino terminal segment. The 18 kDa polypeptide has been identified as the c-phycocyanin alpha chain, a subunit from the peripheral rods of phycobilisomes. Steady-state kinetics show that complexed FNR increases the Km for its substrates in all the electron transfer reactions tested. No success has been achieved in chemical cross-linking of FNR or the complex of FNR: phycobiliproteins with the thylakoids