In this article, we describe for the first time the high-resolution crystal structure of a phenylalanine tRNA synthetase from the pathogenic bacterium Staphylococcus haemolyticus. We demonstrate the subtle yet important structural differences between this enzyme and the previously described Thermus thermophilus ortholog. We also explain the structure-activity relationship of several recently reported inhibitors. The native enzyme crystals were of poor quality-they only diffracted X-rays to 3-5 Å resolution. Therefore, we have executed a rational surface mutagenesis strategy that has yielded crystals of this 2300-amino acid multidomain protein, diffracting to 2 Å or better. This methodology is discussed and contrasted with the more traditional domain truncation approach.
Bibliographical noteFunding Information:
The authors specifically acknowledge the mass-spectroscopic measurements made by Tracy Stevenson and Eric Lund as well as the biophysical experiments conducted by Ronald Sarver and Kimberly Huchings. Use of the IMCA-CAT beamline 17-ID at the APS was supported by the companies of the Industrial Macromolecular Crystallography Association through a contract with the Center for Advanced Radiation Sources at the University of Chicago. Use of the APS was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31-109-Eng-38.
- Antibacterial drug design
- Crystal structure
- Phenylalanine tRNA synthetase
- Protein engineering
- Rational mutagenesis