Extended Data Fig. 10. Mass spectrometry analysis of purified aa682.

a. Intact mass spectrum of aa682 measured by LC-MS. The theoretical mass was 54913 Da, with a measured mass of 54783 Da. The difference in mass would be consistent with loss of the N-terminal methionine. b. LC-MS peptide mapping of aa682. Denatured aa682 was digested with trypsin and chymotrypsin, with the resulting peptide fragments characterized by LC-MS. Trypsin and chymotrypsin peptide fragments mapping to aa682 are indicated below the sequence of aa682 in blue and red respectively. Tryptic peptides could be mapped to 52% of the full-length, while chymotryptic peptides mapping to 94% of aa682. Together, the peptide mapping covered 98% of the expected sequence for aa682.