Crystallization and preliminary x-ray diffraction study of the 3-Fe ferredoxin II from the bacterium Desulfovibrio gigas.

The 3-Fe ferredoxin (FdII) from the bacterium Desulfovibrio gigas has been crystallized at pH 5.0 and 23 degrees C in two different crystal forms. One form is monoclinic, space group C2, with unit cell parameters a = 40.78 A, b = 44.98 A, c = 26.47 A, beta = 104.6 degrees, and one monomer of the FdII tetramer per asymmetric unit. The molecule can be either the monomer of molecular weight 6400 or a dimer of twice this molecular weight with 2-fold symmetry coincident with the 2-fold axis of the crystal. The other crystal form is orthorhombic, space group P2(1)2(1)2 and unit cell parameters a = 109.5 A, b = 37.0 A, c = 30.5 A. The asymmetric unit of this crystal contains two monomers of FdII. The orthorhombic crystal has not been reproduced since the initial crystallization.