1. Department of Virology and Molecular Biology, St. Jude Children’s Research Hospital, Memphis, Tennessee 381011;
2. Center for Macromolecular Crystallography, Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 352942;
3. Department of Virology, Istituto Superiore di Sanita, Rome, Italy3;
4. Department of Biochemistry, School of Pharmaceutical Science, University of Shizuoka, Shizuoka 422, Japan4; and
5. Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, Wisconsin 537065