Reinvestigation of the requirement of cytosolic ATP for mitochondrial protein import.
Protein import into mitochondria requires the energy of ATP hydrolysis inside and/or outside mitochondria. Although the role of ATP in the mitochondrial matrix in mitochondrial protein import has been extensively studied, the role of ATP outside mitochondria (external ATP) remains only poorly characterized. Here we developed a protocol for depletion of external ATP without significantly reducing the import competence of precursor proteins synthesized in vitro with reticulocyte lysate. We tested the effects of external ATP on the import of various precursor proteins into isolated yeast mitochondria. We found that external ATP is required for maintenance of the import competence of mitochondrial precursor proteins but that, once they bind to mitochondria, the subsequent translocation of presequence-containing proteins, but not the ADP/ATP carrier, proceeds independently of external ATP. Because depletion of cytosolic Hsp70 led to a decrease in the import competence of mitochondrial precursor proteins, external ATP is likely utilized by cytosolic Hsp70. In contrast, the ADP/ATP carrier requires external ATP for efficient import into mitochondria even after binding to mitochondria, a situation that is only partly attributed to cytosolic Hsp70.
Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
Takeyoshi
T
Asai
Takashi
T
Takahashi
Masatoshi
M
Esaki
Shuh-ichi
S
Nishikawa
Kenzo
K
Ohtsuka
Masato
M
Nakai
Toshiya
T
Endo
D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D001692:Biological Transport; D003600:Cytosol / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006868:Hydrolysis; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry; D009154:Mutation; D011498:Protein Precursors / Q000737:chemistry; D021381:Protein Transport; D012156:Reticulocytes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology
D018840:HSP70 Heat-Shock Proteins; D024101:Mitochondrial Proteins; D011498:Protein Precursors; D000255:Adenosine Triphosphate; D014357:Trypsin