Figure 3.

Mapping the CheY acetylation sites. (A) HPLC fractionation of CNBr-digested [¹⁴C]CheY-Ac. Radioactive peptides were identified by amino acid sequencing. Fraction 5 did not yield any sequence, whereas fractions 44 and 52 contained the C- and N-terminal CNBr fragments of CheY, respectively. Note that the fraction 52 peak was observed in only one of three independent experiments. (B) Radioactivity released during each cycle of Edman degradation of the peptide in fraction 44 of A. The vertical lines below the radioactivity profile indicate the positions of the six Lys residues in this peptide. The two peaks of radioactivity that rise above background correspond to Lys-92 and Lys-109. The cpm values are relatively modest because only 1% of the material released in each cycle was subjected to scintillation counting.