University of Heidelberg and the German Cancer Research Center 1 article published in JoVE Biology Production of Human Norovirus Protruding Domains in E. coli for X-ray Crystallography Mila M. Leuthold1,2, Anna D. Koromyslova1,2, Bishal K. Singh1,2, Grant S. Hansman1,2 1Schaller Research Group, University of Heidelberg and the German Cancer Research Center, 2Department of Infectious Diseases, Virology, University of Heidelberg Here, we describe a method to express and purify high quality norovirus protruding (P) domains in E. coli for use in X-ray crystallography studies. This method can be applied to other calicivirus P domains, as well as non-structural proteins, i.e., viral protein genome-linked (VPg), protease, and RNA dependent RNA polymerase (RdRp).