1. Department of Molecular Biology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA.
2. Protein Chemistry Technology Center, UT Southwestern Medical Center, Dallas, TX 75390, USA.
3. Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA.
4. Howard Hughes Medical Institute and Department of Biochemistry, UT Southwestern Medical Center, Dallas, TX 75390, USA.