Ferredoxin NADP+ Reductase: Difference between revisions

In many facultatively anaerobic bacteria, this protein acts as an oxygen sensor modifying gene expression that adapts the cell to anaerobic growth. The activity of FNR regulates the cells ability to metabolize aerobically or anaerobically so that when oxygen is abundant, FNR is destabilized and converted into an inactive form. The protein is activated when there are low oxygen tensions. This function is known as transcriptional sensor-regulation. The predominant pathway in which this regulation occurs is through binding or oxidation-reduction of oxygen in the iron sulfur center, in which the iron serves as the initiating cofactor that interacts with the oxygen when it is abundant. This is a reversibly constitutive regulation pathway.

Although facultative anaerobes prefer to use molecular oxygen as the terminal electron acceptor due the high reduction potential, low oxygen stress is able to induce the bacteria to use FNR instead. The transformation involves other proteins such as the sensor regulator system ArcAB, however these regulators are affected by other intermediates. FNR combines the functions of both a sensor and a regulator.

FNR is also an active protein in plants, and is found in the chloroplast and thylakoid membrane of the cell. The FNR reductive mechanism is responsible for the transfer of the final electrons during photosynthesis from photosystem I to NADPH, which then goes on to participate the Calvin cycle as a reducing cofactor.