Reduction of Photosystem I Reaction Center by Recombinant DrgA Protein in Isolated Thylakoid Membranes of the Cyanobacterium Synechocystis sp. PCC 6803

---

I. V. Elanskaya^1*, V. A. Toporova², V. G. Grivennikova¹, E. M. Muronets¹, E. P. Lukashev¹, and K. N. Timofeev¹

¹Faculty of Biology, Lomonosov Moscow State University, 119992 Moscow, Russia; fax: (495) 939-2957; E-mail: ivelanskaya@mail.ru

²Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, 117997 Moscow, Russia; fax: (495) 335-7103; E-mail: toporova@mail.ibch.ru

^* To whom correspondence should be addressed.

Received December 1, 2008; Revision received April 13, 2009

---

To study the function of soluble NAD(P)H:quinone oxidoreductase of the cyanobacterium Synechocystis sp. PCC 6803 encoded by drgA gene, recombinant DrgA protein carrying 12 histidine residues on the C-terminal end was expressed in Escherichia coli and purified. Recombinant DrgA is a flavoprotein that exhibits quinone reductase and nitroreductase activities with NAD(P)H as the electron donor. Using EPR spectroscopy, it was demonstrated that addition of recombinant DrgA protein and NADPH to DCMU-treated isolated thylakoid membranes of the cyanobacterium increased the dark re-reduction rate of the photosystem I reaction center (P700⁺). Thus, DrgA can participate in electron transfer from NADPH to the electron transport chain of the Synechocystis sp. PCC 6803 thylakoid membrane.

---

KEY WORDS: cyanobacteria, drgA gene, NAD(P)H:quinone oxidoreductase, cyclic electron transport around photosystem I, EPR spectroscopy

DOI: 10.1134/S0006297909100034

---