ELECTROSPRAY IONIZATION MASS SPECTROMETRY ANALYSIS OF THE APO- AND METAL-SUBSTITUTED FORMS OF THE FUR PROTEIN

Abstract Fur has been purified and reconstituted with Co 2+ and Mn 2+ . The ESI-MS spectra of the apoprotein as well as Mn-Fur and Co-Fur under acidic denaturating conditions showed the existence of two species of molecular mass 16 660±3 and 16 792±3 Da, which correspond, respectively, to the N-terminal methionine `excised' or `non-excised' forms of the monomer. This result proves the absence of any other post-translational modification or modification due to metal incorporation. On the other hand, under soft conditions, ESI spectra provided for the first time direct evidence for dimeric metal-containing forms in solution.