1. Department of Chemistry, Chemical
Biological Center, Umeå University, 901 87 Umeå, Sweden,
2. Department of Medical Biochemistry
and Biophysics, Chemical Biological Center, Umeå University, 901 87 Umeå, Sweden,
3. Umeå Centre for Microbial
Research, Umeå University, 90187
Umeå, Sweden
4. Department
of Molecular Microbiology, Washington University School of Medicine, St. Louis,
Missouri 63110, United States
5. Department of Molecular, Cellular
and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109-1048, United States