1. Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
2. Institute of Life Sciences, Université catholique de Louvain, B-1348 Louvain-La-Neuve, Belgium
3. Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
4. Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan 48824, United States