Methylglyoxal mediated conformational changes in histone H2A—generation of carboxyethylated advanced glycation end products

Abstract

Methylglyoxal, an oxo-aldehyde has been implicated as a potential precursor in non enzymatic glycation reactions. Its role in the modification of extra cellular proteins has been extensively reported, but little is known about its modification of nuclear proteins, like histones. Here, we report the methylglyoxal induced modification of histone H2A which forms an essential part of intact core nucleosome. In this study commercially available histone H2A was subjected to in vitro non-enzymatic glycation by methylglyoxal. The structural alterations in the histone were characterised by various biophysical and biochemical techniques. The modified histone showed hyperchromicity at 276nm, loss in intrinsic tyrosine fluorescence intensity at 305nm along with a red shift, cross linking and dimer formation in SDS PAGE, induction of α-helix in CD spectroscopy, reduced hydrophobicity in ANS binding studies, accumulation of AGE products, increased carbonyl content, and appearance of a novel peak showing carboxyethylation complemented by a shift in amide I and amide II bands in ATR-FTIR spectroscopy. The modified histone exhibited increased melting temperatures (Tm) and enhanced heat capacities (Cp) in differential scanning calorimetric analysis. The results suggest that methylglyoxal significantly altered the structure of the nuclear histone H2A by non enzymatic glycation reaction. The conformational changes in histone H2A may influence the chromatin integrity which may have implications in various pathological conditions.