1. Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
2. Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
3. Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles CA 90095, USA.
4. Departments of Biological Chemistry and Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles CA 90095, USA.
5. Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA.