Abstract
An examination of metallothionein induction by toxic metal ions reveals that induction is especially prominent by ions with the electronic configurations ( n − 1)d 8, ( n − 1)d 9, ( n − 1)d 10, and ns 2( n − 1)d 10. These electronic configurations are also those of both the ‘softest’ and many of the most toxic of the metal ions. The induction process for this protein appears to be one capable of sensing the electronic configurations of these species through the formation of a trans acting induction complex. The relative ability of toxic heavy metals to induce metallothionein is found to be correlated inversely with their softness parameters, σ p. Examination of the acceptor properties of these inducing ions suggests that an SH or SeH group (soft base) is the critical reactant site for these ions, as these two species form stable bonds with ions that have such electronic configurations. The involvement of SH or SeH in the initial step of the induction process, i.e. as a component of the trans acting element, in a reaction with ions of such electronic configurations would provide the cell with an appropriate response to the presence of species capable of depleting its supply of glutathione, cysteine t-RNA, selenocysteine t-RNA and similar essential species containing SH or SeH. The enchancement of metal ion toxicity in states of selenium deficiency suggests that an SeH containing molecule participates in this step. Two general mechanisms, based on the reaction of inducing metals with selenocysteine t-RNA, are suggested for the initial step in the induction process. The problem of species which are expected on the basis of their electronic configurations to induced MT, but which have not yet been shown to do so is apparently connected with the attempt to use non-labile complexes or extensively hydrolyzed or insoluble compounds as the inducing species.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call