Nif Phenotype of Azotobacter vinelandii UW97 CHARACTERIZATION AND MUTATIONAL ANALYSIS

摘要: Abstract We have identified the molecular basis for nitrogenase negative phenotype exhibited by Azotobacter vinelandii UW97. This strain was initially isolated following nitrosoguanidine mutagenesis. Recently, it shown that this lacks Fe protein activity, which results in synthesis of a FeMo cofactor-deficient apodinitrogenase. Activation apodinitrogenase requires addition both MgATP and wild-type to crude extracts made from A. UW97 (Allen, R. M., Homer, M. J., Chatterjee, R., Ludden, P. W., Roberts, G. P., Shah, V. K.(1993) J. Biol. Chem. 268 23670-23674). Earlier, we proposed sequence events MoFe assembly based on biochemical spectroscopic analysis purified DJ54 (Gavini, N., Ma, L., Watt, G., Burgess, B. K.(1994) Biochemistry 33, 11842-11849). Taken together, these imply process is arrested at same step strains. Since ΔnifH strain, not useful identifying features involved assembly. Here, report systematic an mutant show that, unlike DJ54, nifH gene has no deletion either coding or surrounding sequences. The specific mutation responsible Nif substitution non-conserved serine position 44 phenylalanine as DNA sequencing. Furthermore, oligonucleotide site-directed mutagenesis employed confirm exclusively due residue phenylalanine. By contrast, replacing Ser-44 with alanine did affect vinelandii. Therefore, seems caused general structural disturbance presence bulky 44.