Import and processing of heart mitochondrial cyclophilin D.
Cyclophilins are a family of cyclosporin-A-binding proteins which catalyse rotation about prolyl peptide bonds. A mitochondrial isoform in mammalian cells, cyclophilin D, is a component of the permeability transition pore that is formed by the adenine nucleotide translocase and the voltage-dependent anion channel at contact sites between the inner and outer membrane. This study investigated the submitochondrial location of cyclophilin D by following the fate of radiolabelled protein following import. Precursor [(35)S]cyclophilin D was expressed in vitro from a PCR-generated cDNA. The precursor was imported by rat heart mitochondria and processed in a single step to a 21-kDa protein that was identical (SDS/PAGE) to an in vitro expressed mature protein and a cyclophilin D purified from rat heart mitochondria. No further modification of the mature protein could be demonstrated. Fractionation of mitochondria following import established that cyclophilin D locates only to the matrix. It is concluded that cyclophilin D binding to the permeability transition pore must occur at the inner face of the mitochondrial inner membrane.
Department of Biochemistry and Molecular Biology, University College London, London, UK.
N
N
Johnson
A
A
Khan
S
S
Virji
J M
JM
Ward
M
M
Crompton
D000818:Animals; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins; D018076:DNA, Complementary / Q000378:metabolism; D004072:Digitonin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D020104:Immunophilins / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008929:Mitochondria, Heart / Q000378:metabolism*; D008954:Models, Biological; D016133:Polymerase Chain Reaction; D051381:Rats; D017207:Rats, Sprague-Dawley
D000081406:Peptidyl-Prolyl Isomerase F; D018076:DNA, Complementary; D021983:Cyclophilins; D020104:Immunophilins; D004072:Digitonin