Rubredoxin from Clostridium thermosaccharolyticum. Amino acid sequence, mass-spectrometric and preliminary crystallographic data

Rubredoxin isolated from the thermophilic bacterium Clostridium thermosaccharolyticum has been sequenced and crystallized. The 52-residue sequence is similar to those of rubredoxins occurring in other anaerobic bacteria, but displays some unique features, including a tryptophan residue in position 4, two consecutive proline residues in positions 25 and 26, and an aspartic acid residue in position 41. The molecular mass (5988 Da) of the native rubredoxin has been measured by electrospray-ionization m.s., thus establishing the applicability of the technique to this type of iron-sulphur protein. C. thermosaccharolyticum rubredoxin crystallizes as dark-red elongated prisms with a flat diamond cross-section. The X-ray diffraction shows symmetry consistent with space group P2(1)2(1)2(1). Cell parameters are: a = 2.73 nm, b = 2.98 nm, c = 6.49 nm.