PROTEIN ENGINEERING BY SITE DIRECTED MUTAGENESIS

Abstract

The construction of mutations in the active site of the tyrosyl tRNA synthetase from Bacillus stearothermophilus has allowed us to deduce the relative impörtance of the substrate contacts to transition state binding. The feature dominating the energetics is the exchange reaction with water molecules: thus by deleting a poor H-bonding contact to the substrate we could increase the affinity of the enzyme for substrate. Furthermore by straining the polypeptide backbone by introducing a proline residue, we could improve the interaction of a histidine residue with the substrate. Thus enzymes affinities can be bettered by protein engineering in vitro.