Abstract:

A FeMoco-deficient DnifH Av1 was partially purified from a nifH deleted mutant DJ54 of Azotobacter vinelandii Lipmann grown in NH₃-limited medium. By using the same purification method, DnifE Av1 and NifB^-Av1 were obtained from DJ35 and UW45, respectively. The latter two proteins were obviously much purer than DnifH Av1. Under a suitable condition for crystallization, dark brown short rhombohedron crystals could be obtained from the three proteins. Like NifB^-Av1, the time for formation of DnifH Av1 crystal was longer than that of DnifE Av1. But the optimal concentrations of precipitant and buffer for crystallization of DnifH Av1 were similar to those of DnifE Av1. SDS-PAGE analysis showed that the crystalline DnifH Av1 was similar in the composition to OP Av1. It indicates that the crystal formed in DnifH Av1 solution could be the protein crystal.

Key words: mutant DJ54 of Azotobacter vinelandii , nitrogenase DnifH Av1, crystallization