Biochemical/spectroscopic characterization and preliminary X-ray analysis of a new aldehyde oxidoreductase isolated from Desulfovibrio desulfuricans ATCC 27774

Aldehyde oxidoreductase (AOR) activity has been found in different sulfate reducing organisms (Moura, J. J. G., and Barata, B. A. S. (1994) in Methods in Enzymology (Peck, HI-D., Jr., and LeGall, J., Eds.), Vol. 243, Chap. 4. Academic Press; Romao, M. J., Knablein, J., Huber, R., and Moura, J. J. G. (1997) Frog. Biophys. Mol. Biol. 68, 121-144). The enzyme was purified to homogeneity from extracts of Desulfovibrio desulfuricans (Dd) ATCC 27774, a sulfate reducer that can use sulfate or nitrate as terminal respiratory su bstrates. The protein (AORDd) is described as a homodimer (monomer, circa 1 00 kDa), contains a Mo-MCD pterin, 2 x [2Fe-2S] clusters, and lacks a flavi n group. Visible and EPR spectroscopies indicate a close similarity with th e AOR purified from Desulfovibrio gigas (Dg) (Barata, B. A. S., LeGall, J., and Moura, J. J. G. (1993) Biochemistry 32, 11559-11568). Activity and sub strate specificity for different aldehydes were determined. EPR studies wer e performed in native and reduced states of the enzyme and after treatment with ethylene glycol and dithiothreitol. The AORDd was crystallized using a mmonium sulfate as precipitant and the crystals belong to the space group P 6(1)22, with unit cell dimensions a = b = 156.4 and c = 177.1 Angstrom. The se crystals diffract to beyond 2.5 Angstrom resolution and a full data set was measured on a rotating anode generator. The data were used to solve the structure by Patterson Search methods, using the model of AORDg. (C) 2000 Academic Press.