STRUCTURE OF A MURINE LEUKEMIA-VIRUS RECEPTOR-BINDING GLYCOPROTEIN AT2.0 ANGSTROM RESOLUTION

An essential step in retrovirus infection is the binding of the virus to its receptor on a target cell. The structure of the receptor-bindin g domain of the envelope glycoprotein from Friend murine leukemia viru s was determined to 2.0 angstrom resolution by x-ray crystallography. The core of the domain is an antiparallel beta sandwich, with two inte rstrand loops forming a helical subdomain atop the sandwich, The resid ues in the helical region, but not in the beta sandwich, are highly va riable among mammalian C-type retroviruses with distinct tropisms, ind icating that the helical subdomain determines the receptor specificity of the virus.