1. Department of Chemistry, The Johns Hopkins University, Charles and 34th Streets, Baltimore, Maryland 21218, Kluyver Laboratory for Biotechnology, Delft University of Technology, 2628 BC Delft, The Netherlands, Department of Biochemistry and Molecular Biology, OGI School of Science and Engineering at OHSU, Beaverton, Oregon 97006, and Department of Microbiology and Molecular Genetics, University of California, Los Angeles, California 90095