Abstract
Ferredoxin (Fd) is an electron carrier protein playing a central role in various redox metabolisms in chloroplasts and cyanobacterial cells. Fd forms an electron transfer complex with several enzymes for efficient intermolecular electron transfer. One such enzyme is nitrite reductase (NiR) and its molecular interaction with Fd was investigated by NMR spectroscopy and biochemical techniques, using NiR from cyanobacterium and Fds from cyanobacterium and maize. The cyanobacterial NiR and Fd have a stronger interaction than other combinations, indicative of altered molecular recognition depending on their origin. Based on NMR chemical shift perturbation of 15N-labeled Fds upon complex with NiR, we mapped the interaction area on the 3D structure of each Fd. Two features for the interaction sites were observed; 1) an acidic region in common with both Fds and 2) other regions with subtle differences between them. We presume these characteristics are important to determine the fine molecular recognition.
