FIGURE 5.

Autocatalytic processing of Psd1 is restricted to mitochondria but does not depend on the proper sorting of Psd1. A, ³⁵S-labeled Psd1 precursor was imported in the presence of a membrane potential (Δψ) into wild type mitochondria (MIT) and canine pancreatic microsomes (MIC). P, precursor; i₁, i₂, intermediates 1 and 2; m, mature Psd1β. B, intact, swollen, or lysed (with Triton X-100) mitochondria from a yeast strain expressing Psd1ΔIM were incubated with or without proteinase K (Prot. K). Subsequently, samples were subjected to SDS-PAGE, and proteins were visualized by immunodetection with the indicated antisera. C, ³⁵S-labeled Psd1 or Psd1ΔIM was imported in the presence or absence of a membrane potential (Δψ) into wild type mitochondria. Subsequently, mitochondria were incubated with or without proteinase K. ³⁵S-Labeled proteins were detected by autoradiography. For loading controls, the mitochondrial Hsp70 (Ssc1 (stress-seventy subfamily C/mitochondrial Hsp70)) was immunodetected with specific antibodies. p, precursor; i₁ and i₂, intermediates 1 and 2; m, mature Psd1.