Structural and enzymatic characterization of viper C-type virus

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Retroviruses possess structural polypeptides with varying molecular weights.
• These viruses exhibit intrinsic protein kinase and reverse transcriptase activities.
• Phosphorylation is a key post-translational modification in viral protein function.

Purpose of the Study:

• To investigate the phosphorylation status of viper retroviral structural polypeptides.
• To determine the role of virus-associated protein kinase in viral replication.
• To elucidate the relationship between protein phosphorylation and viral transcription.

Main Methods:

• Purification of viper retroviral structural polypeptides.
• Assay of protein kinase and reverse transcriptase activities.
• In vitro and in vivo phosphorylation studies using ATP and DeoxyATP.
• Sucrose gradient sedimentation for enzyme separation.

Main Results:

• Purified viper retroviral structural polypeptides range from 11,000 to 97,000 daltons, comprising 3 major and 13 minor components.
• Virus-associated protein kinase phosphorylates several structural polypeptides in vitro, but most are not phosphorylated in vivo.
• DeoxyATP is as efficient as ATP in donating phosphate for in vitro protein phosphorylation.
• In vitro protein phosphorylation precedes viral transcription.
• Protein kinase and reverse transcriptase activities show partial separation via sucrose gradient sedimentation.

Conclusions:

• Viral structural polypeptides undergo in vitro phosphorylation, suggesting a regulatory role prior to transcription.
• The in vivo phosphorylation status differs from in vitro findings, indicating complex regulation.
• Protein kinase activity is functionally linked to the initiation of viral transcription.