BioMed Central Page 1 of 13 (page number not for citation purposes) Virology Journal Open Access Research Mutagenesis of the transmembrane domain of the SARS coronavirus spike glycoprotein: refinement of the requirements for SARS coronavirus cell entry Jeroen Corver*, Rene Broer, Puck van Kasteren and Willy Spaan Address: Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, 2300 RC Leiden, the Netherlands Email: Jeroen Corver* -