Fungicide methyl thiophanate binding at sub-domain IIA of human serum albumin triggers conformational change and protein damage

Quaiser Saquib, Abdulaziz A. Al-Khedhairy, Saud A. Alarifi, Sourabh Dwivedi, Jamal Mustafa, Javed Musarrat, Quaiser Saquib, Abdulaziz A. Al-Khedhairy, Saud A. Alarifi, Sourabh Dwivedi, Jamal Mustafa, Javed Musarrat

Index: Int. J. Biol. Macromol. 47(1) , 60-7, (2010)

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Abstract

Fluorescence quenching data on interaction of a fungicide methyl thiophanate (MT) with human serum albumin (HSA) elucidated a primary binding site at sub-domain IIA. Stern–Volmer algorithm and double log plot revealed the binding affinity ( K a) and capacity ( n) of HSA as 1.65 × 10 4 M −1 and 1.0 ( r 2 = 0.99), respectively. Cyclic voltammetric and circular dichroism (CD) studies reaffirmed MT–HSA binding and demonstrated reduction in α-helical content of HSA. Substantial release of the carbonyl and acid-soluble amino groups from MT treated HSA suggested protein damage. The plausible mechanism of methyl ( +CH 3) group transfer from MT to side chain NH group of tryptophan and HSA degradation elucidates the toxicological and clinical implications of this fungicide.