Escherichia coli nitrate reductase subunit A: its role as the catalytic site and evidence for its modification.
Subunits A and B were isolated from purified nitrate reductase by preparative electrophoresis in low levels of sodium dodecyl sulfate. Nonheme iron and low levels of molybdenum were associated with isolated subunit A but not with isolated subunit B. After dialysis against a source of molybdenum cofactor, subunit A regained tightly bound molybdenum and concomitantly regained enzyme activity and reactivity with anti-nitrate reductase antiserum. Subunit B neither bound cofactor nor regained activity or reactivity with antiserum. These data indicate that subunit A contains the active site of the enzyme. Subunit A was also found to be modified posttranslationally in a similar fashion as is subunit B. This was determined by comparison of partial proteolytic digests and amino acid analyses of A subunits from precursor and membrane-bound forms of nitrate reductase.
D000596:Amino Acids / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology*; D005779:Immunodiffusion; D007501:Iron / Q000032:analysis; D046911:Macromolecular Substances; D008982:Molybdenum / Q000032:analysis; D009565:Nitrate Reductases / Q000032:analysis*; D013053:Spectrophotometry
D000596:Amino Acids; D046911:Macromolecular Substances; D008982:Molybdenum; D007501:Iron; D009565:Nitrate Reductases