Interactions between cellular membrane receptors and oncovirus envelope glycoprotein: influence of enzymes and protein-modifying reagents on receptors.

Binding of purified envelope glycoprotein (gp69/71) of Rauscher murine type C oncovirus to cellular membrane receptors has been analyzed with reaction systems using intact cells or membranes of disrupted cells. The reaction was highly specific; only cells permissive to infection by Rauscher virus bound the 125I-labeled viral glycoprotein. The specificity of binding was also demonstrated with respect to virus interference; cells productively infected with murine ecotropic type C virus failed to bind the virus envelope glycoprotein, whereas permissive cells infected with murine xenotropic virus continued to bind the Rauscher ecotropic virus glycoprotein. The reaction required the presence of Ca2+ or Mn2+ and was rapid and reversible. Studies of the enzymatic digestion of membranes suggested that the receptor is a protein which requires lipid either for its activity or for the integrity in the membrane. Receptor binding was greatly reduced by modification of histidine, tyrosine, and tryptophan residues.