tailieunhanh - Báo cáo khoa học: The solution structure of reduced dimeric copper zinc superoxide dismutase

The solution structure of homodimeric Cu2Zn2superoxide dismutase (SOD) of 306 aminoacids was determined on a 13 C, 15N and 70% 2 H labeled sample. Two-thousand eight-hundred and ®ve meaningful NOEs were used, of which 96 intersubunit, and115dihedral angles provideda familyof 30 conformers with an rmsd from the average of and A Ê for the backbone and heavy atoms, respectively. | Eur. J. Biochem. 269 1905-1915 2002 FEBS 2002 doi The solution structure of reduced dimeric copper zinc superoxide dismutase The structural effects of dimerization Lucia Banci Ivano Bertini Fiorenza Cramaro Rebecca Del Conte and Maria Silvia Viezzoli Department of Chemistry and Centro Risonanze Magnetiche University of Florence Italy The solution structure of homodimeric Cu2Zn2 superoxide dismutase SOD of 306 aminoacids was determined on a 13C 15N and 70 2H labeled sample. Two-thousand eighthundred and five meaningful NOEs were used of which 96 intersubunit and 115 dihedral angles provided a family of 30 conformers with an rmsd from the average of and A for the backbone and heavy atoms respectively. When the rmsd is calculated for each subunit the values drop to and Ay for the backbone and heavy atoms respectively. The two subunits are identical on the NMR time scale at variance with the X-ray structures that show structural differences between the two subunits as well as between different molecules in the unit cell. The elements of secondary structure . eight b sheets are the same as in the X-ray structures and are well defined. The odd loops I III and V are well resolved as well as loop II located at the subunit interface. On the contrary loops IV and VI show some disorder. The residues of the active cavity are well defined whereas within the various subunits of the X-ray structure some are disordered or display different orientation in dif ferent X-ray structure determinations. The copper I ion and its ligands are well defned. This structure thus represents a well defined model in solution relevant for structure-function analysis of the protein. The comparison between the solution structure of monomeric mutants and the present structure shows that the subunit-subunit interactions increase the order in loop II. This has the consequences of inducing the structural and dynamic properties .