Cyclophilin a binds to peroxiredoxins and activates its peroxidase activity.
Six distinct peroxiredoxin (Prx) proteins (Prx I-VI) from distinct genes have been identified in mammalian tissues. Prxs are members of a group of peroxidases that have conserved reactive cysteine residue(s) in the active site(s). An immediate physiological electron donor for the peroxidase catalysis for five Prx proteins (Prx I-V) has been identified as thioredoxin (Trx), but that for Prx VI (1-Cys Prx) is still unclear. To identify an immediate electron donor and a binding protein for Prx VI, we performed a Prx VI protein overlay assay. A 20-kDa binding protein was identified by the Prx VI protein overlay assay with flow-through fractions from a High-Q column with rat lung crude extracts. Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) and MS-Fit, we identified the 20-kDa Prx VI-binding protein as a cyclophilin A (CyP-A). The binding of recombinant human CyP-A (hCyP-A) to Prx VI was confirmed by using the hCyP-A protein overlay assay and Western immunoblot analysis with hCyP-A-specific antibodies. hCyP-A enhanced the antioxidant activity of Prx VI, as well as the other known mammalian Prx isotypes. hCyP-A supported antioxidant activity of Prx II and Prx VI both against thiol (dithiothreitol)-containing metal-catalyzed oxidation (MCO) systems and ascorbate-containing MCO systems. Prx II was reduced by hCyP-A without help from any other reductant, and the reduction was cyclosporin A-independent. These results strongly suggest that CyP-A not only binds to Prx proteins but also supports its peroxidase activity as an immediate electron donor. In addition, Cys(115) and Cys(161) of hCyP-A were found to be involved in the activation and the reduction of Prx.
Lee
S P
SP
Department of Biological Science, Chonnam National University, Gwangju, Korea 500-757, the Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea 135-270.
Hwang
Y S
YS
Kim
Y J
YJ
Kwon
K S
KS
Kim
H J
HJ
Kim
K
K
Chae
H Z
HZ
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology; D001665:Binding Sites; D015153:Blotting, Western; D002384:Catalysis; D021984:Cyclophilin A / Q000494:pharmacology*; D016572:Cyclosporine / Q000494:pharmacology; D003545:Cysteine / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism*; D054465:Peroxiredoxin VI; D054464:Peroxiredoxins; D011485:Protein Binding; D011487:Protein Conformation; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013347:Subcellular Fractions; D013997:Time Factors
D000975:Antioxidants; D011994:Recombinant Proteins; D016572:Cyclosporine; D010544:Peroxidases; D054465:Peroxiredoxin VI; D054464:Peroxiredoxins; D021984:Cyclophilin A; D003545:Cysteine; D001205:Ascorbic Acid