Identification of a phosphorylated site in Sbh1p by mass spectrometry. Sec complex was purified using membranes from an SSS1-HA tagged strain as in Methods. The Sbh1p band was excised, digested with trypsin, and the resulting peptides analyzed by mass spectrometry. The amino acid sequence of Sbh1p is shown. Peptides covered in the analysis are shown in pink. Trypsin cleavage sites are underlined. Peaks corresponding to the phosphorylated peptide are indicated. Note that S27 is the only potential phosphate acceptor site in the Sbh1p cytosolic domain not covered by this analysis.