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Sequence-specific antibodies show that maturation of Moloney leukemia virus envelope polyprotein involves removal of
Abstract:
We followed maturation of the glycosylated envelope polyprotein Pr80env of a murine retrovirus by using antisera specific to subregions of the protein, including an antiserum directed against a synthetic peptide corresponding to the COOH-terminus of Pr80env. Shortly after synthesis and glycosylation, Pr80env is cleaved into two species, gp70 and Pr15E, that are found associated, perhaps through disulfide bonds, in infected cells. Pr15E is further cleaved at the time of virus maturation to form virus protein p15E. NH2-Terminal protein sequence analysis showed that Pr15E had an NH2 terminus in common with p15E. Pr15E, but not p15E, is precipitated by antibody against the COOH-terminal peptide; hence, p15E is missing a peptide at the COOH-terminus. Our data indicate that Pr15E is the predominant species in cells and p15E is the major species in virus.
Insights
Murine retrovirus envelope polyprotein maturation was tracked. The study found Pr15E is the main cellular form, while p15E is the major viral form, indicating a COOH-terminal cleavage during maturation.
Area of Science:
- Virology
- Molecular Biology
- Protein Chemistry
Background:
- Retroviral envelope glycoproteins are crucial for viral entry and assembly.
- Understanding the maturation process of these proteins is key to deciphering viral replication cycles.
Purpose of the Study:
- To elucidate the maturation pathway of the murine retrovirus envelope polyprotein, Pr80env.
- To identify the intermediate and final cleavage products and their locations within infected cells and virions.
Main Methods:
- Utilized antisera specific to different subregions of Pr80env, including one against a synthetic COOH-terminal peptide.
- Performed NH2-terminal protein sequence analysis.
- Investigated protein association using precipitation assays.
Main Results:
- Pr80env is synthesized and glycosylated, then cleaved into gp70 and Pr15E, which remain associated in infected cells.
- Pr15E undergoes further cleavage during virus maturation to yield p15E.
- NH2-terminal sequencing confirmed a shared terminus between Pr15E and p15E.
- Antibody precipitation revealed that p15E lacks the COOH-terminal peptide present in Pr15E.
- Pr15E is the predominant species in cells, whereas p15E is the major species found in the virus.
Conclusions:
- The maturation of Pr80env involves a sequential cleavage process.
- Pr15E is a key intermediate, and its subsequent cleavage results in the loss of a COOH-terminal peptide to form the mature viral protein p15E.
- These findings provide insights into the structural changes of retroviral envelope proteins during maturation and their localization.