Ferredoxin-quinone reductase

Absorbance transients have been observed in isolated thylakoids which could be identified to originate from the reduction of FNR to the semireduced FNR by PSl. Generation of FNR appears to occur unperturbed in the absence of Fd. Role of Fd and the Fd FNR complex, its dynamic properties under various experimental conditions as well as the role of ferredoxin quinone reductase (FQR) are currently investigated. 

The immediate electron acceptor for P700 is a special molecule of chlorophyll. This unique Chi a (Aq) rapidly passes the electron to a specialized quinone (Aj), which in turn passes the e to the first in a series of membrane-bound ferredoxins (Fd, Chapter 21). This Fd series ends with a soluble form of ferredoxin, Fd, which serves as the immediate electron donor to the fiavo-protein (Fp) that catalyzes NADP reduction, namely, ferredoxin NADP reductase. 

FIGURE 21. Photosystem I (PS I). P700, special pair Q, plastoquinone QH2, dihy-droplastoquinone NADP, nicotinamide adenine dinucleotide phosphate FQR, ferre-doxin-quinone reductase FNR, ferredoxin-NADP reductase Fd, ferredoxin ADP, adenosine diphosphate ATP, adenosine triphosphate. 

Rarely termed ferredoxin reductase, PSI is excited maximally by 700 run light, and produces 2 FdREo per 2 PCred oxidised. The electrons are passed from P700 through a series of quinones and iron-sulfur centres to the iron-containing... 

---