Phosphorylation sites detected in the Shs1 protein

Two independent digestions (trypsin and chymotrypsin) were performed on Shs1 gel bands, which resulted in high sequence coverage and redundant and therefore more reliable phosphorylation site identifications. Phosphorylation sites are denoted in the peptide sequence by an asterisk. When MS/MS spectra did not contain enough fragment ions to unambiguously assign the phosphorylation site within the peptide sequence, all possibly modified amino acids are grouped in parenthesis in column 1 and also the most likely position is indicated in column 2, followed by alternate positions in parenthesis. The column labeled “In vitro (partial)” refers to the partially phosphorylated form of Shs1 generated in vitro. The column labeled “In vitro (full)” refers to the fully phosphorylated form of Shs1 generated in vitro.