CRYSTALLIZATION AND PRELIMINARY-X-RAY STUDIES OF NITROGENASE COMPONENT-1 (THE MOFE PROTEIN) FROM KLEBSIELLA-PNEUMONIAE

Two crystal forms of component 1 (the MoFe protein) of nitrogenase fro m Klebsiella pneumoniae have been isolated and characterized. The tric linic form has cell dimensions a = 76.0, b = 109.6, c = 144.6 Angstrom , alpha = 80.3, beta = 74.9 and gamma = 69.6 degrees, diffracts to aro und 3.0 Angstrom and has two molecules in the asymmetric unit. The mon oclinic form belongs to space group P2(1) with a = 76.6, b = 127.8, c = 109.1 Angstrom and beta = 104.6 degrees (frozen at 100K), diffracts to 1.5 Angstrom and has one molecule in the asymmetric unit. At this r esolution the outstanding questions concerning the structure and the o peration of the enzyme, in particular the linkage between the Fe4S4 un its in the P clusters, the true geometry of the apparently trigonal Fe atoms in the FeMoco and the reduction site itself, should be answerab le.