Comparison of active and inactive forms of iron protein from Rhodospirillum rubrum

Abstract

The Fe protein of nitrogenase from R. rubrum was purified in its active and inactive forms. The inactive form exists as a 2 subunit modified form of the enzyme. In contrast, the active form exists as a single-subunit unmodified form of the enzyme. The upper subunit (on sodium dodecyl sulfate/polyacrylamide gel electrophoresis) of the inactive form contained at least the phosphate group of the covalently bound modifying group. The active and inactive forms of the enzyme were identical proteins on the basis of amino acid composition, tryptic digest pattern and immunological cross-reactivity.