Figure 3.

Translocation of Small Human Presecretory Proteins into the ER Lumen Involves Sec63

(A) SEC63 siRNA effects on ppl, Sec61β, ppa, ps, and respective variants.

(B) Murine SEC63 knockout effects on ppl, Sec61β, ppa, ps, and DHFR hybrids.

(C–H) Plasmid complementation of SEC63 siRNA effects.

(C) ppl.

(D) Sec61β.

(E) ppa.

(F) ps.

(G) ppa-DHFR.

In (A)–(G), HeLa cells were transfected with SEC63-UTR siRNA and the indicated plasmids. Precursors were co- or post-incubated with the indicated ER membranes and analyzed by SDS-PAGE and phosphorimaging.

(H) Sec63 protein content of the HeLa cells, complemented as indicated, relative to β-actin was validated by western blot and the control sample was set to 100%.

(I) Sec63 protein content of HeLa cells, depleted as indicated, relative to β-actin was validated by western blot and the control sample was set to 100%.

(J) Sec63 interactions and SEC63 mutants (red) used in the complementation assay.

Shown are individual data points of at least three independent experiments and the mean. Statistical significance (^∗∗∗p < 0.001, ^∗∗p < 0.01, ^∗p < 0.05) was tested by Student’s t test (upper panel) or using ANOVA plus post hoc Dunnett or Newman-Keuls multiple comparison test (horizontal brackets).

See also Figures S2 and S3.