1. Department of Pathology, Microbiology and Immunology; School of Medicine; Vanderbilt University; Nashville TN 37232 USA
2. Department of Molecular Biosciences and the Proteomics Center of Excellence; Northwestern University; 2145 N. Sheridan Road Evanston IL 60208 USA
3. Department of Biochemistry; School of Medicine; Vanderbilt University; Nashville TN 37232 USA
4. Department of Biochemistry and Molecular Biophysics; Howard Hughes Medical Institute; Columbia University; New York NY 10032 USA
5. Department of Biological Sciences; Columbia University; New York NY 10027 USA
6. Department of Biological Chemistry and Molecular Pharmacology; Harvard Medical School; Boston MA 02115 USA
7. Department of Chemistry; Vanderbilt University; Nashville TN 37235 USA