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Polypeptides of Mason-Pfizer monkey virus. III. Translational order of proteins on the gag and env gene specified
Abstract:
Mason-Pfizer monkey virus (M-PMV), the prototype D-type retrovirus, unlike most retroviruses, preassembles core structures in the cytoplasm of infected cells during morphogenesis. We have shown previously (J. Bradac and E. Hunter, 1984, Virology 138, 260-275) that M-PMV virions contain 5 gag-encoded polypeptides. In this report, the translational order of the proteins encoded on the gag and env genes of M-PMV has been determined by pactamycin mapping. The proposed order of the viral proteins on their respective precursors is env: NH2-gp85-gp20-COOH; gag: NH2-p10-pp24/pp16-p12-p27-p14-COOH. Myristic acid-labeled virions contained a single radioactive protein, p10, supporting the mapping of this molecule to the amino terminus. From these studies it is clear that M-PMV contains an unusual additional gag polypeptide, p12, for which no function has been assigned to date. A remarkable similarity exists in the size and organization of M-PMV and mouse mammary tumor virus (MMTV) gag polypeptides; suggesting a common ancestor to these two viruses.
Insights
Mason-Pfizer monkey virus (M-PMV) retrovirus research reveals the order of gag and env proteins. M-PMV contains an unusual gag polypeptide, p12, and shares similarities with mouse mammary tumor virus (MMTV).
Area of Science:
- Virology
- Molecular Biology
- Retroviral Research
Background:
- Mason-Pfizer monkey virus (M-PMV) is a D-type retrovirus known for cytoplasmic core structure assembly.
- Previous studies identified five gag-encoded polypeptides in M-PMV virions.
Purpose of the Study:
- To determine the translational order of proteins encoded by the gag and env genes of M-PMV.
- To characterize the M-PMV gag polypeptide composition and identify potential functional roles.
Main Methods:
- Pactamycin mapping was employed to elucidate the translational order of viral proteins.
- Myristic acid labeling was used to identify the amino-terminal protein in virions.
Main Results:
- The translational order for env proteins is NH2-gp85-gp20-COOH, and for gag proteins is NH2-p10-pp24/pp16-p12-p27-p14-COOH.
- Myristic acid labeling confirmed p10 as the amino-terminal gag protein.
- An additional gag polypeptide, p12, was identified in M-PMV, with its function currently unknown.
Conclusions:
- The study clarifies the protein organization within M-PMV, identifying a novel gag polypeptide.
- The findings suggest a potential evolutionary relationship between M-PMV and mouse mammary tumor virus (MMTV) due to similarities in gag polypeptide size and organization.