Interactions of retroviral structural proteins with single-stranded nucleic acids

Area of Science:

• Biochemistry
• Molecular Biology
• Virology

Background:

• Retroviral structural proteins play crucial roles in viral assembly and RNA binding.
• Understanding these interactions is key to developing antiviral strategies.

Purpose of the Study:

• To quantitatively analyze the binding interactions between murine leukemia virus (MuLV) structural proteins (p10, p10', Pr65gag) and single-stranded polyribonucleotides.
• To compare the RNA-binding properties of MuLV p10 with Rous sarcoma virus (RSV) pp12.

Main Methods:

• Utilized fluorescence enhancement of poly(epsilon A) and tryptophan fluorescence quenching assays to monitor protein-RNA association.
• Determined stoichiometric binding, occluded site size (n), and intrinsic association constant (K) under varying salt concentrations.
• Investigated the effect of chemical modifications on protein-RNA binding affinity.

Main Results:

• MuLV p10 binds stoichiometrically to single-stranded RNA with an occluded site size (n) of approximately 6 residues.
• RSV pp12 also binds to poly(epsilon A) with n = 5 +/- 1.
• MuLV p10 binding to poly(epsilon A) is noncooperative at 0.06 M NaCl, with K = 2.3 X 10(6) M-1.
• Pr65gag exhibits a higher affinity for poly(epsilon A) compared to p10.
• Chemical modification of p10 cysteine residues did not affect its RNA binding affinity.

Conclusions:

• MuLV p10 and RSV pp12 demonstrate specific stoichiometric binding to single-stranded RNA.
• The binding affinity and stoichiometry are influenced by salt concentration.
• Pr65gag is a high-affinity RNA-binding protein, suggesting a significant role in viral processes.