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In vitro binding of purified murine ecotropic retrovirus envelope surface protein to its receptor, MCAT-1
R A Davey1, C A Hamson, J J Healey
1Howard Hughes Medical Institute, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Abstract:
An amino-terminal portion of the Friend murine leukemia virus (MLV) envelope surface protein [SU, residues 1 to 236 [SU:(1-236)]] and its receptor, MCAT-1, were each purified from insect cells after expression by using recombinant baculoviruses. Friend SU:(1-236) bound specifically to Xenopus oocytes that expressed MCAT-1 with an affinity (Kd, 55 nM) similar to that of viral SU binding to permissive cells. Direct binding of Friend SU:(1-236) to purified MCAT-1 was observed in detergent and after reconstitution into liposomes. Analysis of binding demonstrated that MCAT-1 and Friend SU:(1-236) interact with a stoichiometry of near 1:1. These findings demonstrate that the amino-terminal domain from the SU of ecotropic murine retroviruses contains an MCAT-1 binding domain.
Insights
Researchers purified the Friend murine leukemia virus (MLV) envelope protein SU:(1-236) and its receptor MCAT-1. They found this MLV protein portion directly binds MCAT-1, identifying a key viral interaction domain.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Murine leukemia viruses (MLVs) are retroviruses that utilize specific host cell receptors for entry.
- The envelope surface protein (SU) of MLVs mediates binding to cellular receptors.
- Understanding these interactions is crucial for deciphering viral tropism and developing antiviral strategies.
Purpose of the Study:
- To investigate the binding interaction between an amino-terminal portion of the Friend MLV SU protein and its receptor, MCAT-1.
- To characterize the biophysical properties of this interaction, including affinity and stoichiometry.
- To identify the MCAT-1 binding domain within the Friend MLV SU protein.
Main Methods:
- Expression and purification of Friend MLV SU:(1-236) and MCAT-1 using recombinant baculoviruses in insect cells.
- Binding assays using Xenopus oocytes expressing MCAT-1.
- Direct binding studies of purified SU:(1-236) and MCAT-1 in detergent solution and reconstituted liposomes.
Main Results:
- Friend MLV SU:(1-236) specifically bound to MCAT-1 expressing Xenopus oocytes with high affinity (Kd, 55 nM).
- Direct binding was confirmed between purified SU:(1-236) and MCAT-1 in both detergent and liposomal environments.
- The interaction between SU:(1-236) and MCAT-1 occurred at a near 1:1 stoichiometry.
Conclusions:
- The amino-terminal domain of the Friend MLV SU protein (residues 1-236) contains a functional MCAT-1 binding domain.
- This study validates MCAT-1 as a direct binding partner for a specific region of the MLV envelope protein.
- These findings contribute to the understanding of ecotropic murine retrovirus-receptor interactions.