Figure 1.

Suppression of the doa4 degradation defect by did mutations. Deg1-βgal pulse-chase analysis in doa4-1 and did doa4-1 mutants. Average Deg1-βgal half-lives from one to five independent measurements were as follows: wild type, 11 min; did1-1 doa4-1, 13 min; did2-1 doa4-1, 12 min; did4-1 doa4-1, 14 min; and did5-1 doa4-1, 22 min. Half-lives were calculated from quantitative Phosphorimager data from time points up to 30 min. During this time, degradation is close to first order; as described originally by Hochstrasser and Varshavsky (1990), Deg1-βgal degradation rates slow gradually, particularly with long chase times. The reporter protein was expressed from a chromosomally integrated copy of Deg1-lacZ. 90 kD indicates a proteolytic fragment of Deg1-βgal generated in cells in which the reporter protein is short-lived.