The solution structure of a [3Fe-4S] ferredoxin: oxidised ferredoxin II from Desulfovibrio gigas

The use of standard 2D NMR experiments in combination with 1D NOE experimen ts allowed the assignment of 51 of the 58 spin systems of oxidised [3Fe-4S] ferredoxin isolated from Desulfovibrio gigas. The NMR solution structure w as determined using data from 1D NOE and 2D NOESY spectra, as distance cons traints, and information from the X-ray structure for the spin systems not detected by NMR in torsion angle dynamics calculations to produce a family of 15 low target function structures. The quality of the NMR family, as jud ged by the backbone r.m.s.d. values, was good (0.80 Angstrom), with the maj ority of phi/psi angles falling within the allowed region of the Ramachandr an plot. A comparison with the X-ray structure indicated that the overall g lobal fold is very similar in solution and in the solid state. The determin ation of the solution structure of ferredoxin II (FdII) in the oxidised sta te (FdII(ox)) opens the way for the determination of the solution structure of the redox intermediate state of FdII (FdII(int)), for which no X-ray st ructure is available.