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Interaction of trialkyltin(IV) chlorides with sarcoplasmic reticulum calcium ATPase
Author(s) -
GarcíaCarrillo Scheherezade,
Aranda Francisco J.,
Ortiz Antonio,
Teruel José A.
Publication year - 2012
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.2903
Subject(s) - chemistry , tributyltin , calcium atpase , calcium , atpase , endoplasmic reticulum , cooperativity , biophysics , stereochemistry , biochemistry , enzyme , organic chemistry , biology
The interaction of the organotin compounds trimethyltin(IV) and tributyltin(IV) chlorides with the calcium pump from sarcoplasmic reticulum membranes was studied. It was found that the presence of calcium fully protects against the inhibitory effect of both organotin compounds. However, the apparent affinity of the protein for tributyltin chloride is two orders of magnitude higher than for trimethyltin chloride ( K 0.5 values of 14 µ m and 1.4 m m , respectively). Studies of intrinsic fluorescence of the Ca 2+ ‐ATPase and enzyme phosphorylation by ATP and Pi support the hypothesis that the inhibitory properties of trialkyltin compounds are due to the inhibition of calcium binding to the high‐affinity binding sites of the Ca 2+ ‐ATPase. This suggests that there is a specific interaction between the trialkyltin compounds and the calcium binding sites of the protein. The effect of trialkyltin compounds on Ca 2+ ‐ATPase was also addressed by differential scanning calorimetry to assess the thermal transition of the protein denaturation, and by infrared spectroscopy in the absorption region corresponding to the amide I band (1600–1700 cm −1 ) to observe changes in the secondary structure of the protein. We conclude that the interaction of trialkyltin compounds with Ca 2+ ‐ATPase reduces the affinity and cooperativity for calcium binding and, consequently, the inhibition of ATPase activity. These events are accompanied by changes in the secondary structure of the protein, including loss of α‐helix structure and a concomitant increase in protein aggregation or unfolding. The activity of trialkyltin compounds on the Ca 2+ ‐ATPase is discussed in relation to their solubility in water and in the lipid phase. Copyright © 2012 John Wiley & Sons, Ltd.