title: Structural study of the copper and zinc sites in metallothioneins by using extended X-ray-absorption fine structure.
abstract: Zn-metallothionein 1 from rabbit liver was investigated by means of Zn K-edge extended X-ray-absorption fine structure (e.x.a.f.s.). Also, the Cu and Zn K-edge e.x.a.f.s. were measured for two samples of mixed Cu Zn-metallothionein 2, with Cu/Zn ratios of 5:2 and 6:3, from pig liver. Detailed simulation of the Cu sites shows a primary co-ordination with three sulphur atoms, presumably from cysteine residues at 0.225 nm +/- 0.001 nm (2.25 +/- 0.01 A). The data for the Zn sites are best reproduced by four Zn-S separations at 0.233 +/- 0.001 nm (2.33 +/- 0.01 A). The Zn K-edge e.x.a.f.s. recorded for rabbit metallothionein 1 at 77 K shows, in addition to the primary co-ordination shell, evidence for two Zn-Zn separations at approx. 0.50 nm (5.0 A). This latter result provides the first information concerning the internal arrangement of zinc atoms in Zn7-metallothionein.
mesh_terms: D000818:Animals; D003300:Copper / Q000032:analysis*; D008099:Liver / Q000032:analysis; D008668:Metallothionein; D008956:Models, Chemical; D011487:Protein Conformation; D011817:Rabbits; D013057:Spectrum Analysis; D013552:Swine; D014965:X-Rays; D015032:Zinc / Q000032:analysis*
chemical_list: D003300:Copper; D008668:Metallothionein; D015032:Zinc