Extended Data Fig. 4: Mass spectrometric characterization of intact proteins.

Intact protein mass spectra obtained from purified MfR2 proteins. Inactive protein (top) and active protein (bottom). Insets represent the decharged and deisotoped mass as calculated by the program Protein Deconvolution (version 4.0) using the ReSpect algorithm therein. The result from the deconvolution of n = 30 consecutive scans in one LC–MS run per protein form is shown. Each protein form was analysed in duplicate LC–MS runs. Protein intact masses are given as mean ± s.d. The s.d. was 1.4 Da for the inactive protein and 2 Da for the active form. The results show that the active protein is 17 ± 2 Da heavier than the inactive MfR2.