Role of Protein Electronstatics on the Post-transfer Editing Function of Escherichia coli, Prolyl-tRNA Synthetase

Abstract

Prolyl-tRNA synthetases (ProRSs) are class II synthetases that catalyze covalent attachment of proline to the 3'-end of the tRNAPro. ProRSs from all three kingdoms of life have shown to misactivate noncognate alanine and cysteine, and form mischarged aminoacyl-tRNAPro. The insertion domain (?180 amino acids) of Escherichia coli ProRS is the post?transfer editing active site that hydrolyzes specifically mischarged alanyl-tRNAPro. The highly conserved lysine 279 (K279) in the insertion domain is critical for the post-transfer editing reaction and previous studies have shown that mutation of this lysine to alanine is detrimental to the post-transfer editing function of the enzyme. The exact mechanism through which K279 catalyzes the post-transfer editing reaction has remained poorly understood. In an attempt to gain insight into the mechanism of post-transfer editing reaction of Escherichia coli ProRS, the pKa calculations of the K279 have been performed using combined quantum mechanical and molecular mechanical (QM/MM) simulations. Herein, we report the effect of charged residues on the pKa of K279 and thereby, on the post-transfer editing function of Escherichia coli prolyl-tRNA synthetase.