Structure of the electron transfer complex between ferredoxin and ferredoxin-NADP(+) reductase

Area of Science:

• Biochemistry
• Structural Biology
• Photosynthesis Research

Background:

• Oxygenic photosynthesis relies on electron carriers like ferredoxin (Fd) interacting with oxidoreductases.
• Fd-NADP(+) oxidoreductase (FNR) is a key enzyme in utilizing photosynthetically derived reducing equivalents.

Purpose of the Study:

• To determine the first crystal structure of the complex between maize leaf Fd and FNR.
• To elucidate the molecular interactions and structural basis for electron transfer between Fd and FNR.

Main Methods:

• X-ray crystallography to obtain the complex structure.
• Nuclear Magnetic Resonance (NMR) spectroscopy to confirm solution-state interactions.

Main Results:

• The crystal structure reveals close proximity (6.0 A) between the Fd 2Fe-2S cluster and FNR's flavin adenine dinucleotide (FAD).
• Intermolecular interactions are primarily electrostatic (salt bridges) with a hydrophobic interface near the redox centers.
• Fd binding induces structural changes in FNR's active site, including a new hydrogen bond.

Conclusions:

• The determined structure provides a molecular basis for efficient electron transfer between Fd and FNR.
• Observed structural communication suggests a mechanism for modulating FNR's enzymatic activity.
• This research enhances understanding of photosynthetic electron transport chains.