1. Department of Biophysical Chemistry, NIZO, PO Box 20, 6710 BA Ede, The Netherlands.,
2. Harvard Medical School, Department of Biological Chemistry and Molecular Pharmacology, LHRRB, 200 Longwood Avenue, Boston, MA 02146, USA.,
3. Department of Microbiology, Wageningen Agricultural University, H. van Suchtelenweg 4, 6703 CT Wageningen, The Netherlands.