Investigation of the Interaction of Triethyltin with Rat Liver Mitochondria Using Binding Studies and Mössbauer Spectroscopy

TLDR: The assignment of the absorption doublet, from triethyltin in the high affinity site environment, to a four coordinated triethygtin-mitochondrial membrane complex is suggested by the investigation of some intramolecularly coordinated triorganotin compounds.

Abstract: 1 The binding of triethyltin to rat liver mitochondria is measured and the results indicate the presence of a three component system. This involves triethyltin binding to two specific sites, one of high affinity, which is found to have a concentration similar to that found for the F1-ATPase complex and one of lower affinity. The third component is attributed to partition of triethyltin into the mitochondrial membrane. 2 Non-specific partition is shown by inhibition of triethyltin binding to the low affinity site with N-ethylmaleimide and to the high affinity site by buffer pH values lower than pH 5.7. Combination of these two conditions leaves a Scatchard plot which can be interpreted as being due to triethyltin partitioned into the mitochondrial membrane. 3 The selective inhibition of triethyltin binding to the low affinity site by N-ethylmaleimide preincubation indicates the presence of a thiol group in the low affinity site and the absence of N-ethylmaleimide-reactive thiol groups necessary for triethyltin binding in the high affinity site. 4 Mossbauer spectra of triethyltin bound to mitochondria also seem to be derived from the same three component system. N-Ethylmaleimide preincubation assigns an absorption doublet to low affinity bound triethyltin and the concentration dependence of the absorption intensities assigns a second doublet to partitioned triethyltin. 5 Washing triethyltin pretreated mitochondria leaves an absorption doublet which is assigned to high affinity bound triethyltin. This assignment is confirmed by binding and ATPase activity studies before and after this washing procedure. 6 Triethyltin bound to the high and low affinity sites is found, by the ratio of the Mossbauer quadrupole splitting and the isomer shift obtained, to be four coordinate or possibly cis-five coordinate. 7 The assignment of the absorption doublet, from triethyltin in the high affinity site environment, to a four coordinated triethyltin-mitochondrial membrane complex is suggested by the investigation of some intramolecularly coordinated triorganotin compounds.