ROLE OF NIFS IN MATURATION OF GLUTAMINE PHOSPHORIBOSYLPYROPHOSPHHATE AMIDOTRANSFERASE

Glutamine phosphoribosylpyrophosphate amidotransferase from Bacillus s ubtilis is synthesized as an inactive precursor that requires two matu ration steps: incorporation of a [4Fe-4S] center and cleavage of an 11 -residue NH2-terminal propeptide. Overproduction from a multicopy plas mid in Escherichia coli leads to the formation of soluble proenzyme an d mature enzyme forms as well as a small fraction of insoluble proenzy me. Heterologous expression of Azotobacter vinelandii nifS From a comp atible plasmid increased the maturation of the soluble proenzyme three -to fourfold without influencing the content of the insoluble fraction . These results support a role for NifS in heterologous Fe-S cluster a ssembly and enzyme maturation.