1. Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut 06536;
2. Center for Structural Systems Biology, University Medical Center Hamburg-Eppendorf and Deutsches Elektronen-Synchrotron, 20246 Hamburg, Germany
3. Institute of Molecular Biotechnology GmbH, Austrian Academy of Sciences, and
4. Research Institute of Molecular Pathology, A-1030 Vienna, Austria
5. Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, 72076 Tübingen, Germany