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Characterization of Rauscher murine leukemia virus envelope glycoprotein receptor in membranes from murine
Abstract:
Plasma membrane preparations from KA31 (mouse) cells contained receptors for the binding of Rauscher murine leukemia virus (R-MuLV) envelope glycoprotein, gp70. This binding was demonstrated by gel filtration of a mixture of the microsomal fraction of the cells and 125I-labeled gp70. A rapid and convenient assay was developed to measure the complex formation between the membrane receptors and gp70 involving specific precipitation of the complex by 3 to 4% polyethylene glycol. The complex formation was responsive to the concentrations of both the receptor and gp70 and also to changes in temperature and pH. The gp70 binding was a noncooperative, saturable process, and an association constant of 3.5 X 10(8) M-1 was estimated from the binding data. The complex formation was reversible and a near-total exchange of 125I-labeled gp70 in the complex was achieved by incubation with excess of unlabeled gp70. The complex formation was inhibited by protein denaturing agents, guanidine-hydrochloride and urea. Pretreatment of the membrane fractions with either chymotrypsin or phospholipase C led to a loss of the membrane-associated receptor activity, indicating that a lipoprotein structure was important for the receptor function, consistent with the observation that nonionic detergents strongly inhibited the complex formation.
Insights
Mouse cells possess receptors that bind Rauscher murine leukemia virus (R-MuLV) envelope glycoprotein gp70. This interaction is saturable and reversible, indicating specific molecular recognition.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Rauscher murine leukemia virus (R-MuLV) is a retrovirus known to infect mouse cells.
- Understanding virus-receptor interactions is crucial for developing antiviral strategies.
Purpose of the Study:
- To identify and characterize receptors on mouse cells that bind the R-MuLV envelope glycoprotein gp70.
- To develop a quantitative assay for measuring gp70-receptor complex formation.
Main Methods:
- Plasma membrane preparations from KA31 mouse cells were used.
- Binding assays involved 125I-labeled gp70 and gel filtration.
- Complex formation was measured using polyethylene glycol precipitation.
- Binding kinetics and inhibition studies were performed.
Main Results:
- Receptors for R-MuLV gp70 were identified on mouse cell membranes.
- A rapid assay using polyethylene glycol precipitation was established.
- gp70 binding was concentration-dependent, saturable, and reversible.
- An association constant of 3.5 X 10(8) M-1 was determined.
- Receptor activity was sensitive to temperature, pH, and protein-denaturing agents.
Conclusions:
- Mouse cell membranes contain specific receptors for R-MuLV gp70.
- The receptor-gp70 interaction is a saturable, reversible, and noncooperative process.
- The receptor is likely a lipoprotein, as indicated by sensitivity to proteases, phospholipase C, and detergents.