1. National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, USA
2. European Molecular Biology Laboratory, Heidelberg, Germany
3. Tokyo Institute of Technology, Midoriku, Yokohama, Kanagawa, Japan
4. Stowers Institute for Medical Research, Kansas City, Missouri, USA, and Department of Microbiology, Kansas University Medical Center, Kansas City, Kansas, USA