FIGURE 3 

Typical examples of extremely regulated proteins. (A) The panel on the left side shows the extracted ion chromatograms of the ¹⁴N- and ¹⁵N-labeled version of the DIDIEYHQNK peptide from Hsp26p, which could only be detected in the ion chromatogram of the carbon-limited culture (¹⁴N version). The panel on the right shows the extracted ion chromatograms of the ¹⁴N- and ¹⁵N-labeled GTMITLNDR peptide from Asp3p. This peptide is only present in the nitrogen-limited yeast culture (¹⁵N version). (B) Extracted ion chromatograms from the same peptides as in panel A are shown for the reverse labeling experiment. In this experiment, the nitrogen-limited culture was grown on ¹⁴N media and the carbon-limited culture on ¹⁵N-labeled media.