Extracellular superoxide dismutase exists as an octamer.
Human extracellular superoxide dismutase (EC-SOD) is involved in the defence against oxidative stress induced by the superoxide radical. The protein is a homotetramer stabilised by hydrophobic interactions within the N-terminal region. During the purification of EC-SOD from human aorta, we noticed that material with high affinity for heparin-Sepharose formed not only a tetramer but also an octamer. Analysis of the thermodynamic stability of the octamer suggested that the C-terminal region is involved in formation of the quaternary structure. In addition, we show that the octamer is composed of both aEC-SOD and iEC-SOD folding variants. The presence of the EC-SOD octamer with high affinity may represent a way to influence the local concentration of EC-SOD to protect tissues specifically sensitive to oxidative damage.
Due
Anne V
AV
Center for Insoluble Protein Structures (inSPIN), Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
Petersen
Steen V
SV
Valnickova
Zuzana
Z
Østergaard
Louise
L
Oury
Tim D
TD
Crapo
James D
JD
Enghild
Jan J
JJ
D001011:Aorta / Q000201:enzymology; D019281:Dimerization; D006801:Humans; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D021381:Protein Transport; D012685:Sepharose / Q000031:analogs & derivatives; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
C037405:heparin-sepharose; D012685:Sepharose; C441642:SOD3 protein, human; D013482:Superoxide Dismutase