1. University of Tennessee, Department of Biochemistry, Cellular and Molecular Biology, 1414 W. Cumberland Avenue, Knoxville, TN 37966, USA.
2. University of Chicago, Department of Biochemistry and Molecular Biology, 929 E. 57th Street, Chicago, IL 60637, USA.
3. FOM Institute for Atomic and Molecular Physics, Science Park 104, Amsterdam, 1098 XG, The Netherlands.
4. Institut Pasteur, Biology of Gram‐Positive Pathogens, Department of Microbiology, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France.
5. CNRS, URA 2172, F‐75015 Paris, France.