Figure 6
Example high resolution MS1 scans of H2A.X-F 1–31. Shown are high resolution MS1 scans of various PTM states seen on the [M + 4H]+4 ions of the 1–31 residue, chymotrypsin-generated peptides of H2A.X-F1 and -F2 from egg and pronuclei. All ions exhibiting a charge state of +4 are labeled. As an example, in panel A, differences of 14 Da, 56 Da, and 80 Da are noted to represent the addition of methylations/acetylations, priopionylations (Kpr and Spr), and phosphorylations, respectively. Note that H2As are 100% α-N-terminally acetylated and in the absence of acetylation, lysines are propionylated. Since the Δm for an acetylation is 42 Da while the Δm for a priopionylation is 56 Da, the K5ac form of the peptide appears at a lower mass than the α-N-acetylated (‘unmodified’) form of the peptide. Also note that serine residues can be propionylated at low levels. (A) H2A.X-F1 from egg. (B) H2A.X-F1 from pronuclei. (C) H2A.X-F2 from egg. (D) H2A.X-F2 from pronuclei.