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Translational readthrough of an amber termination codon during synthesis of feline leukemia virus protease
Abstract:
Feline leukemia virus contains a protease which apparently has the same specificity as murine leukemia virus protease. It cleaves in vitro the Pr65gag of Gazdar-mouse sarcoma virus into the constituent p15, p12, p30, and p10 proteins. We purified the protease and determined its NH2-terminal amino acid sequence (the first 15 residues). Alignment of this amino acid sequence with the nucleotide sequence (I. Laprevotte, A. Hampe, C. H. Sherr, and F. Galibert, J. Virol. 50:884-894, 1984) reveals that the protease is a viral-coded enzyme and is located at the 5' end of the pol gene. As previously found for murine leukemia virus (Y. Yoshinaka, I. Katoh, T. D. Copeland, and S. Oroszlan, Proc. Natl. Acad. Sci. U.S.A. 82:1618-1622, 1985), feline leukemia virus protease is synthesized through in-frame suppression of the gag amber termination codon by insertion of a glutamine in the fifth position, and the first four amino acids are derived from the gag gene.
Insights
Feline leukemia virus protease cleaves viral proteins, similar to its murine counterpart. This viral-coded enzyme is located in the pol gene and synthesized via gag gene suppression.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Feline leukemia virus (FeLV) is a significant pathogen in cats.
- Viral proteases are crucial for processing viral polyproteins into functional proteins.
- Murine leukemia virus (MuLV) protease shares specificity with other retroviral proteases.
Purpose of the Study:
- To characterize the protease of Feline Leukemia Virus (FeLV).
- To determine the enzymatic specificity and genetic location of the FeLV protease.
- To elucidate the synthesis mechanism of the FeLV protease.
Main Methods:
- In vitro cleavage assays using Gazdar-mouse sarcoma virus Pr65gag substrate.
- Purification of the FeLV protease.
- Determination of the NH2-terminal amino acid sequence of the protease.
- Alignment of amino acid sequence with viral nucleotide sequence.
Main Results:
- FeLV protease exhibits similar cleavage specificity to MuLV protease.
- The protease cleaves Pr65gag into mature proteins: p15, p12, p30, and p10.
- FeLV protease is a viral-coded enzyme located at the 5' end of the pol gene.
- Synthesis involves in-frame suppression of the gag amber termination codon, with the first four amino acids from the gag gene.
Conclusions:
- FeLV protease is a viral-encoded enzyme with conserved specificity among leukemia viruses.
- Its location within the pol gene and unique synthesis pathway are key features.
- Understanding FeLV protease function is vital for developing antiviral strategies.