Escherichia coli nitrate reductase subunit A: its role as the catalytic site and evidence for its modification.

AUTOR(ES)

Chaudhry, G R

RESUMO

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.

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