Structure solution and molecular dynamics refinement of the yeast Cu,Zn enzyme superoxide dismutase

Cu,Zn yeast superoxide dismutase was crystallized from polyethylene glycol solutions. The crystals belong to the P2(1)2(1)2 space group, with cell dimensions a = 105.3, b = 143.0, c = 62.1 A; two dimers of Mr = 32,000 each are contained in the asymmetric unit. Diffraction data at 2.5 A resolution were collected with the image-plate system at the EMBL synchrotron radiation facility in Hamburg. The structure was determined by molecular replacement using as a search model the 'blue-green' dimer of the bovine Cu,Zn superoxide dismutase. The crystallographic refinement of the molecular replacement solution was performed by means of molecular dynamics techniques and resulted in an R factor of 0.268 for the data between 6.0 and 2.5 A. The model was subsequently subjected to conventional restrained crystallographic refinement of the coordinates and temperature factors. The current R value for the data between 6.0 and 2.5 A is 0.220. Owing to the large radius of convergence of the molecular dynamics-crystallographic refinement, the convergence of the refinement process was reached after 18.1 ps of simulation time. The geometry of the active site of the enzyme appears essentially preserved compared with the bovine superoxide dismutase. The beta-barrel structure in the yeast enzyme is closed at the upper part by an efficient hydrogen-bonding scheme

La Nuova Galles (del Sud) la terra Vittoria (Australia Felice) e l'isola di Diemen [cartographic material].

Map of southeastern Australia showing Tasmania, Victoria and New South Wales extending into Queensland. Relief shown by hachures.; In upper left margin: Marmocchi.; In lower right margin: G. Bonatti inc. Torino.; Prime meridian: Ferro.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.map-rm3698

Succinylated copper, zinc superoxide dismutase. A novel approach to the problem of active subunits

Bovine erythrocyte superoxide dismutase (BESOD) has been extensively succinylated with succinic anhydride. Succinylated BESOD has an identical electron paramagnetic resonance (EPR) spectrum but only 10% as much activity as the native enzyme, showing that an increase of the negative charge of the protein surface lowers the activity without alteration of the active site structure. On the other hand, sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gel electrophoresis indicates that interaction between subunits is strongly weakened by succinylation. NaDodSO4 has no effect on either the activity or EPR spectrum of the protein. BESOD was immobilized by coupling to a Sepharose matrix with no alteration of the EPR spectrum. Succinylation of the immobilized protein led to detachment from the gel of approximately 50% of the molecules, as estimated by parallel EPR measurements of the gel and activity determinations on the eluate. It is concluded the succinylation leads to dissociation of BESOD into nondenatured subunits, having lower activity than the native protein possibly because of charge effects on the enzyme-O2-interaction

Succinylated copper, zinc superoxide dismutase. A novel approach to the problem of active subunits

Bovine erythrocyte superoxide dismutase (BESOD) has been extensively succinylated with succinic anhydride. Succinylated BESOD has an identical electron paramagnetic resonance (EPR) spectrum but only 10% as much activity as the native enzyme, showing that an increase of the negative charge of the protein surface lowers the activity without alteration of the active site structure. On the other hand, sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gel electrophoresis indicates that interaction between subunits is strongly weakened by succinylation. NaDodSO4 has no effect on either the activity or EPR spectrum of the protein. BESOD was immobilized by coupling to a Sepharose matrix with no alteration of the EPR spectrum. Succinylation of the immobilized protein led to detachment from the gel of approximately 50% of the molecules, as estimated by parallel EPR measurements of the gel and activity determinations on the eluate. It is concluded the succinylation leads to dissociation of BESOD into nondenatured subunits, having lower activity than the native protein possibly because of charge effects on the enzyme-O2-interaction