Binding characteristics of Rauscher leukemia virus envelope glycoprotein gp71 to murine lymphoid cells

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Abstract
The major envelope glycoprotein (gp71) purified from Rauscher leukemia virus (R-MuLV) binds efficiently to murine [mouse] lymphoid cell but not to murine nonlymphoid cells or lymphoid cells from other species. Binding of 125I-labeled R-MuLV gp71 was competitively inhibited by unlabeled glycoprotein, by whole R-MuLV, but not by murine xenotropic viruses, R-MuLV p30 and several unrelated proteins. Polyacrylamide gel electrophoresis profiles of iodinated gp71 after binding to lymphoid cells were similar to prebound profiles. Antibody to R-MuLV gp71 prevented binding, whereas normal serum had no effect. Adsorption of the glycoprotein to murine lymphoid cells occurs rapidly and is time and temperature dependent. The procedure described is sensitive for detecting the binding activity of approximately 104 cells. Binding was proportional up to 2.5 .times. 15 cells/ml and plateaued above 107 cells/ml. In the presence of excess R-MuLV gp71, BALB/c thymocytes bound approximately 2.4 .times. 104 molecules/cell.