Under a suitable condition of crystallization, dark brown rhombohedron crystals (the lengths of the longest two diagonals were 0.25 and 0.12 mm, respectively) could be obtained from nitrogenase CrFe protein purified from a mutant UW3 of Azotobacter vinelandii Lipmann grown in Cr containing but NH3 free medium. The possibility of crystallization, as well as the number, size and quality of crystals obviously depended on the concentrations of PEG 8000, MgCl2, NaCl, Tris and Hepes buffer, and methods of crystallization. The optimum concentrations of the chemicals for crystallization of CrFe protein were slightly different from those for crystallization of MnFe protein from UW3 grown in Mn and ΔnifZ MoFe protein from a nifZ deleted strain of A. vinelandii. The crystal seemed to be formed from CrFe protein.
固氮酶铬铁蛋白的晶体生长
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