Figure 5. Glycans A and B are required for ER export.

(A) Wild-type cells highly expressing aBCD-CPY*, AbCD-CPY*, abCD-CPY*, and abcD-CPY* were used in in vitro vesicle budding assays as described in Figure 3. Each data set is from three independent experiments with the standard deviation represented by error bars. Statistical significance was determined using Student's paired t-test (aBCD-CPY*, AbCD-CPY*, or abCD-CPY* vs. abcD-CPY*, p<0.05). (B) Δpep4 cells highly expressing glycan variants in panel A were pulse-labeled for 10 min with [³⁵S]methionine/cysteine and chased as indicated. Substrate proteins were immunoprecipitated, separated by SDS-PAGE, and visualized by phosphorimaging. The position of hyperglycosylated forms is indicated. (C) Transport deficient glycan variants are toxic. Wild type cells carrying CPY* (ABCD) and glycan variant genes were assayed for cytotoxicity following induction as described in Figure 3C.