1. Institute of Biochemistry and Biology, University of Potsdam, D-14476 Potsdam, Germany, Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, 97078 Würzburg, Germany, Helmholtz Center for Infection Research, 38124 Braunschweig, Germany, and Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11794-5215