Reverse Transcriptase in Action: FRET-Based Assay for Monitoring Flipping and Polymerase Activity in Real Time.

Area of Science:

• Biochemistry
• Molecular Biology
• Virology

Background:

• Human immunodeficiency virus-1 reverse transcriptase (HIV-1 RT) is crucial for viral replication and a primary target for antiretroviral therapy.
• Current HIV-1 RT inhibitors face challenges due to poor resistance profiles, necessitating the development of new drugs.
• Existing assays for HIV-1 RT activity are often endpoint measurements, limiting real-time analysis of enzyme dynamics.

Purpose of the Study:

• To develop a continuous, real-time assay for measuring HIV-1 RT binding orientation and polymerase activity.
• To utilize Förster resonance energy transfer (FRET) and steady-state fluorescence spectroscopy for direct assessment of enzyme-substrate interactions.
• To differentiate between nucleoside and non-nucleoside RT inhibitors and determine their potency.

Main Methods:

• Development of a novel Förster resonance energy transfer (FRET)-based assay using conventional steady-state fluorescence spectroscopy.
• Monitoring changes in RT binding orientation and primer elongation in real-time.
• Distinguishing enzyme activity and inhibitor effects based on kinetics and fluorescence changes.

Main Results:

• The FRET assay successfully measured HIV-1 RT binding orientation and polymerase activity in real-time.
• Distinct fluorescence changes and kinetics allowed for separate visualization of binding orientation and primer elongation.
• The assay effectively discriminated between nucleoside and non-nucleoside RT inhibitors, determining their potency.

Conclusions:

• The developed FRET assay provides a simple, continuous, and real-time method for studying HIV-1 RT.
• This assay is an improved alternative to current screening methods for discovering new anti-HIV drugs.
• The assay's ability to classify inhibitors in a single step facilitates drug development and resistance profiling.