Fig. 3: Role of the Sec31 CTD.

a Domain organisation of wild-type Sec31, and the ΔCTD mutant. b Slices through different z heights of a binned and filtered representative cryo-tomogram of COPII-coated tubule formed with Sec31-ΔCTD. Arrowheads as in Fig. 1a. The outer coat appears partially disordered. Scale bar 50 nm. These images are representative of tubes from 47 tomograms. c Top panels: slices through xy and yz planes of 8× binned subtomogram average of rods extracted from wild-type tubules. Orange arrowheads indicate the appendage density in Fig. 2d. Red arrowhead indicates the vertex, and beige is the membrane. Bottom panels. The same slices for the average of rods extracted from tubules formed with Sec31-ΔCTD. Extra density is absent, confirming its assignment to Sec31 CTD. The density for the vertex and membrane is also fainter, indicating overall disorder of rods in this sample. Scale bar 10 nm. d Left panel: a sec31Δ yeast strain transformed with the indicated plasmids was tested on 5-FOA, revealing lethality associated with deletion of the CTD. Right panel: the same plasmids were transformed into a sec31Δ emp24Δ yeast strain revealing rescue of viability. A representative result is shown from at least three replicates.