Parameters that influence the binding of human immunodeficiency virus reverse transcriptase to nucleic acid...

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Human immunodeficiency virus reverse transcriptase (HIV-RT) is a key enzyme in viral replication.
• Understanding HIV-RT's interaction with nucleic acid substrates is crucial for developing antiviral therapies.

Purpose of the Study:

• To investigate the binding kinetics of HIV-RT to different nucleic acid hybrid structures (RNA-DNA and DNA-DNA).
• To determine the influence of magnesium ions (Mg2+) on HIV-RT binding affinity and stability.

Main Methods:

• HIV-RT binding assays using pre-incubation with nucleic acid substrates and a 'trap' polymer to measure dissociation.
• Kinetic analysis of association (k(on)) and dissociation (k(off)) rate constants, and equilibrium dissociation constants (Kd).
• Evaluation of binding to RNA-DNA and DNA-DNA hybrids with varying recessed termini, in the presence and absence of Mg2+.

Main Results:

• HIV-RT exhibited more stable binding to RNA-DNA hybrids compared to DNA-DNA substrates, with higher k(off) and Kd values for DNA-DNA.
• The primary difference in binding stability was attributed to slower dissociation rates (k(off)) for RNA-DNA hybrids.
• Magnesium ions significantly stabilized HIV-RT binding to DNA-DNA structures, decreasing k(off) by 20-60 fold and k(on) by up to 100 fold for specific substrates.

Conclusions:

• HIV-RT binding affinity is sequence and structure-dependent, favoring RNA-DNA hybrids.
• Magnesium ions play a critical role in stabilizing HIV-RT interactions with DNA-DNA substrates, impacting enzyme function.
• These findings have implications for understanding HIV replication mechanisms and designing targeted therapeutics.