Impact of tyrosine nitration at positions Tyr307 and Tyr335 on structural dynamics of Lipoprotein-associated phospholipase A 2 -A therapeutically important cardiovascular biomarker for atherosclerosis.

Protein tyrosine nitration (PTN) is a post translational event which results in the generation of 3-Nitrotyrosine (3-NT). High levels of 3-NT were reported in several human diseases such as Parkinson's disease, Alzheimer's disease, amylotrophic lateral sclerosis and coronary artery disease. It was reported that PTN at positions 307 and 335 of Lipoprotein-associated phospholipase A2 (Lp-PLA2 ) curtails its enzymatic activity but the mechanism of inhibition at the structure level is still incomprehensible. The present study is an in silico endeavor to understand nitrative stress induced structural changes in Lp-PLA2. Molecular docking studies revealed a decreased binding affinity of substrate, Platelet Activating Factor (PAF) with the nitrated forms of Lp-PLA2 (NT-Tyr307 and NT-Tyr335) compared to the wild type, due to differences in the hydrogen bond interaction patterns. Molecular dynamics (MD) simulation studies suggests higher flexibility of nitrated forms compared to wild type, disorientation of the catalytic triad and decreased molecular interactions of NT-Tyr307 and NT-Tyr335 with other residues of the protein. Essential dynamics (ED) further confirmed the enhanced structural flexibility of nitrated forms of Lp-PLA2 . Our findings would help understand the molecular mechanism of nitrative stress induced inhibition of Lp-PLA2 which may further assist in designing of therapeutics having protective functions against PTN.