1. Department of Structural Biology; St. Jude Children's Research Hospital; 332 N. Lauderdale Memphis TN 38105
2. Department of Biochemistry; University of Tennessee; 858 Madison Ave. Memphis TN 38163
3. Department of Biochemistry; University of Utah School of Medicine; Salt Lake City UT 84132
4. School of Biological Sciences; University of Sussex; Falmer Brighton BN1 9QG United Kingdom
5. MRC Laboratory of Molecular Biology; Hills Rd. Cambridge CB2 2QH United Kingdom