[1] Leibniz Inst Expt Virol, Notkestr 85, D-22607 Hamburg, Germany
[2] Univ Hamburg, Dept Struct Cell Biol Viruses, CSSB, Notkestr 85, D-22607 Hamburg, Germany
[3] Univ Oxford, Wellcome Ctr Human Genet, Div Struct Biol, Roosevelt Drive, Oxford OX3 7BN, England
[4] Hannover Med Sch, Inst Virol, Struct Virol Grp, Carl Neuberg Str 1, D-30625 Hannover, Germany