Fig. 4.

Identification of the nitration site in recombinant tagged methionine synthase 1 from Arabidopsis. (A) Equal amounts (5 μg) of recombinant AtMS1 protein were nitrated (+) or not (–), separated by one-dimensional SDS–PAGE, and blotted onto nitrocellulose to be probed by western blot with anti-3-nitroY (anti-3NY) antibodies. After stripping, membranes were further probed with anti-5×His antibodies. Molecular size markers are shown on the left side of the panels. (B) MS/MS spectrum of nitrated YLFAGVVDGR peptide from AtMS1. The insert shows the detected y and b series as well as a detail of the spectrum showing the immonium ion corresponding to nitrated Y (C).