HIV-1 reverse transcriptase-pseudoknot RNA aptamer interaction has a binding affinity in the low picomolar range...

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• Systematic evolution of ligands by exponential enrichment (SELEX) identifies high-affinity oligonucleotides for protein targets.
• These oligonucleotides, including aptamers, show potential as chemotherapeutics by inhibiting pathogenic proteins.
• Human immunodeficiency virus 1 reverse transcriptase (HIV-1 RT) is a key target for antiviral therapies.

Purpose of the Study:

• To biochemically characterize the interaction between an HIV-1 RT and a SELEX-derived pseudoknot RNA aptamer.
• To elucidate the binding mechanism and specificity of the RNA aptamer for HIV-1 RT.

Main Methods:

• Site-directed spin-labeling and Electron Paramagnetic Resonance (EPR) spectroscopy to study enzyme conformation.
• Kinetic analysis to determine association and dissociation rates.
• Equilibrium binding studies to measure dissociation constant (K(d)).

Main Results:

• The aptamer binds to a 'closed' conformation of HIV-1 RT.
• A two-step binding process was observed, with slow dissociation rates from the enzyme.
• An exceptionally low K(d) of approximately 25 pM was determined, indicating high-affinity binding.
• The aptamer demonstrated high specificity for HIV-1 RT, with significantly lower affinity for HIV-2 RT.

Conclusions:

• The pseudoknot RNA aptamer exhibits potent and specific inhibition of HIV-1 RT.
• The slow dissociation rate contributes to the high affinity and therapeutic potential of the aptamer.
• This aptamer represents a promising candidate for developing novel anti-HIV-1 chemotherapeutics.