Open AccessDifferent Transport Pathways of Individual Precursor Proteins in Mitochondria
Author(s) -
ZIMMERMANN Richard,
HENNIG Bernd,
NEUPERT Walter
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb05357.x
Subject(s) - mitochondrion , oligomycin , biochemistry , neurospora crassa , cytochrome c , protein subunit , neurospora , biology , atpase , oxidative phosphorylation , cytochrome , atp synthase , microbiology and biotechnology , enzyme , gene , mutant
Transport of mitochondrial precursor proteins into mitochondria of Neurospora crassa was studied in a cellfree reconstituted system. Precursors were synthesized in a reticulocyte lysate programmed with Neurospora mRNA and transported into isolated mitochondria in the absence of protein synthesis. Uptake of the following precursors was investigated: apocytochrome c , ADP/ATP carrier and subunit 9 of the oligomycin‐sensitive ATPase. Addition of high concentrations of unlabelled chemically prepared apocytochrome c (1–10 μM) inhibited the appearance in the mitochondrial of labelled cytochrome c synthesized in vitro because the unlabelled protein dilutes the labelled one and because the translocation system has a limited capacity [apparent V is 1–3 pmol × min −1 × (mg mitochondrial protein) −1 ]. Concentrations of added apocytochrome c exceeding the concentrations of precursor proteins synthesized in vitro by a factor of about 10 4 did not inhibit the transfer of ADP/ATP carrier or ATPase subunit 9 into mitochondria. Carbonylcyanide m ‐chlorophenylhydrazone, an uncoupler of oxidative phosphorylation, inhibited transfer in vitro of ADP/ATP carrier and of ATPase subunit 9, but not of cytochrome c . These findings suggest that cytochrome c and the other two proteins have different import pathways into mitochondria. It can be inferred from the data presented that different ‘receptors’ on the mitochondrial surface mediate the specific recognition of precursor proteins by mitochondria as a first step in the transport process.