1. Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, United States
2. Natural Products Research Institute, College of Pharmacy, Seoul National University, San 56-1, Sillim, Seoul 151-742, Republic of Korea
3. Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
4. Biological Institute, Section for Ecology and Evolution, University of Copenhagen, Universitetsparken 15, Building 12, 2100 Copenhagen Ø, Denmark