Covalent modification of the iron protein of nitrogenase from Rhodospirillum rubrum by adenosine diphosphoribosylation of a specific arginine residue.

Abstract

Nitrogenase in R. rubrum is inactivated in vivo by the covalent modification of the Fe protein with a nucleotide. The preparation of 2 modified peptides derived from proteolytic digestion of the inactive Fe protein is described. The modifying group is shown to be adenosine diphosphoribose, linked through the terminal ribose to a guanidino nitrogen of arginine. The structural features were established by using proton and phosphorus NMR, positive- and negative-ion fast at bombardment mass spectrometry, and fast atom bombardment/collisionally activated decomposition mass spectrometry. Spectral methods along with chromatographic analysis and sequential degradation established the sequence of the modification site of Fe protein as Gly-Arg(ADR-ribose)-Gly-Val-Ile-Thr. This corresponds to the sequence in the Fe protein from Azotobacter vinelandii for amino acid residues 99-104.