Reconstitution of apo-superoxide dismutase by nitric oxide-induced copper transfer from metallothioneins.
Little is known about copper transfer from Cu-metallothionein (Cu-MT) to various target proteins, such as apo-SOD, and the potential role of redox mechanisms in this transfer. We studied Cu transfer from Cu-MT to apo/Zn-SOD in a cell-free model system and found that Cu(5)-MT and Cu(10)-MT were able to reconstitute SOD activity only in the presence of a nitric oxide donor, (Z)-[N-(3-ammoniopropyl)-N-(n-propyl)amino]diazen-1-ium++ +-1,2-diolate (NOC-15). The percentage of reconstitution by Cu(5)-MT and Cu(10)-MT was 34 and 83%, respectively, compared with that reconstituted by free Cu alone. A Cu chelation assay using bathocuproine disulfonate (BCS) showed that NOC-15 induced release of free Cu from Cu(10)-MT but not from Cu(5)-MT. The transfer of Cu from Cu-MT to apo/Zn-SOD was not accompanied by enhanced Cu-dependent generation of ascorbate radicals or hydroxyl radicals as measured by EPR spectroscopy. We found a 70% decrease in the number of 2,2'-dithiodipyridine titratable SH groups on MT after incubation with NOC-15. Overall, our results suggest that Cu-MT could potentially function in a nitric oxide-dependent pathway for the delivery of Cu to apo-SOD in copper-challenged cells.
Liu
S X
SX
Department of Environmental & Occupational Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15238, USA.
Fabisiak
J P
JP
Tyurin
V A
VA
Borisenko
G G
GG
Pitt
B R
BR
Lazo
J S
JS
Kagan
V E
VE
D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism; D001384:Azetidines / Q000378:metabolism; D003300:Copper / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D017665:Hydroxyl Radical / Q000378:metabolism; D008668:Metallothionein / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000378:metabolism; D011817:Rabbits; D013482:Superoxide Dismutase / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
C111679:1-(N-(3-ammoniopropyl)-N-(n-propyl)amino)diazen-1-ium-1,2-diolate; D001384:Azetidines; D018832:Molecular Chaperones; D020030:Nitric Oxide Donors; C007121:copper thionein; C021267:zinc thionein; D009569:Nitric Oxide; D017665:Hydroxyl Radical; D003300:Copper; D008668:Metallothionein; D013482:Superoxide Dismutase; D015032:Zinc; D001205:Ascorbic Acid