Gem1 is a negative regulator of mitochondrial–nuclear heme trafficking. Heme trafficking rates were monitored using the SA pulse-chase assay and rate constants calculated, as described in Fig. 2, for (A,B) gem1Δ, (C,D) mdm12Δ, (E,F) mdm34Δ, (G,H) psd1Δ, (I,J) ypt7Δ, and (K,L) vps39Δ cells. Data represent the mean±s.d. of independent triplicate cultures. *P<0.05, **P<0.01, ***P<0.001 (one-way ANOVA with Dunnett's post-hoc test).