Preferential covalent binding of acetaldehyde to the α-chain of purified rat liver tubulin†

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Abstract
Hepatic ethanol oxidation generates the reactive intermediate acetaldehyde, which binds to proteins. Previous work, using bovine brain tubulin as a model protein, has shown that acetaldehyde preferentially formed stable adducts on the α-chain of the heterodimeric molecule. This binding resulted in functional impairment of the tubulin/microtubule system as evidenced by a decreased ability of adducted tubulin to form microtubules. Since tubulin/microtubules are believed to be very important cytoskeletal components of the hepatocyte and results with brain tubulin were interesting, our goal was to extend these studies to liver tubulin. We purified tubulin from rat liver by a polymerization-based cycle method followed by phosphocellulose chromatography. We then characterized the covalent binding of [14C]acetaldehyde to liver tubulin. Naturally forming and cyanoborohydride-stimulated stable adducts formed linearly with liver tubulin in a manner almost identical to that with brain tubulin. We also found that the α-chain of the native heterodimeric liver tubulin molecule was the preferred site of adduct formation at low acetaldehyde to protein ratios. These results confirm and extend our previous findings with the brain tubulin model and further suggest that the α-chain of tubulin may be a preferential site for acetaldehyde-adduct formation during ethanol oxidation in the liver.

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