The interaction of cadium-induced rat renal metallothionein with bivalent mercury in vitro.
Addition of Hg2+ in vitro to metallothionein (Cd : Cu : Zn = 6.5 : 4 : 1) from the kidneys of Cd2+ exposed rats appears to result initially in the replacement of Zn2+, then Cd2+ and finally copper. The ionic stoichiometries between Hg2+-binding and the release of Cd2+ (or Zn2+) and copper are 3 : 2 and 1 : 1 respectively. After treatment with amounts of Hg2+ sufficient to displace completely either the bound Zn2+ and Cd2+, or all of the original cations, the metallothionein has little or no negative charge at pH 8.0 and is not resolved into the two isometallothioneins, which characterize the (Cd, Cu, Zn)-thionein, by ion exchange chromatography at this pH. Cation substitution occurs in both isometallothioneins and there is no evidence that Hg2+ interacts preferentially with one of them. Treatment of the metallothionein with increasing amounts of Hg2+, equivalent to approx. 25% and 50% of the bound cations gives rise to a range of molecular species of progressively decreasing negative charge. The consistent stiochiometry between Hg2+ uptake and Cd2+ or Zn2+ release at all concentrations of Hg2+ indicates that free thiol groups are not formed during the substitution reaction.
D000818:Animals; D001665:Binding Sites; D002104:Cadmium / Q000494:pharmacology*; D055598:Chemical Phenomena; D002621:Chemistry; D003300:Copper / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008628:Mercury / Q000378:metabolism*; D008667:Metalloproteins / Q000378:metabolism*; D008668:Metallothionein / Q000378:metabolism*; D051381:Rats; D013438:Sulfhydryl Compounds / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
D008667:Metalloproteins; D013438:Sulfhydryl Compounds; D002104:Cadmium; D003300:Copper; D008668:Metallothionein; D008628:Mercury; D015032:Zinc