Subunit-selective mutagenesis indicates minimal polymerase activity in heterodimer-associated p51 HIV-1 reverse...

Area of Science:

• Biochemistry
• Molecular Biology
• Virology

Background:

• HIV-1 reverse transcriptase (RT) is a crucial enzyme for viral replication.
• RT exists as a heterodimer composed of p66 and p51 subunits.
• The polymerase active site, containing critical aspartic acid residues, is essential for RT function.

Purpose of the Study:

• To investigate the functional roles of the p66 and p51 subunits in HIV-1 RT activity.
• To determine the importance of specific aspartic acid residues in the polymerase active site of each subunit.

Main Methods:

• Purification of reconstituted, recombinant HIV-1 RT heterodimers.
• Selective mutation of aspartic acid residues in the polymerase active site of either p66 or p51 subunits.
• Assessment of RNA-dependent DNA polymerase and ribonuclease H (RNaseH) activities.

Main Results:

• Mutations in the p51 subunit's active site did not significantly alter RNA-dependent DNA polymerase or RNaseH activity.
• Mutations in the p66 subunit's active site abolished RNA-dependent DNA polymerase activity but retained wild type RNaseH activity.
• The p51 subunit cannot compensate for the loss of polymerase activity due to mutations in the p66 subunit.

Conclusions:

• The aspartic acid residues in the p66 subunit are critical for the RNA-dependent DNA polymerase activity of HIV-1 RT.
• The p51 subunit does not play a direct catalytic role in polymerase activity.
• These findings highlight the distinct functional contributions of the p66 and p51 subunits in the HIV-1 RT heterodimer.