Figure 2.

Tim22 and Tim54 require different outer membrane receptors for their import into mitochondria. In vitro synthesized ³⁵S-labeled Tim22 (left panel), Tim54 (middle panel), and Su9-DHFR (right panel) were imported into mitochondria isolated from wild-type (WT), tom70Δ, tom20Δ, or tom5Δ yeast cells for the indicated times in the presence (lanes 1–4, 6–9, and 11–14) or absence (lanes 5, 10, and 15) of a membrane potential (Δψ). Samples were treated with proteinase K before SDS-PAGE analysis. Radiolabeled proteins were detected by storage phosphorimage cassette technology and quantitated using ImageQuant software (Molecular Dynamics). The import observed in wild-type mitochondria after 20 min was set at 100% (control).