fd gene 5 protein binds to double-stranded polydeoxyribonucleotides poly(dA.dT) and poly[d(A-T).d(A-T)]

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• fd gene 5 protein (G5P) is known to bind nucleic acids.
• Understanding protein-DNA interactions is crucial for comprehending genetic processes.
• Previous studies have investigated G5P binding to various nucleic acid forms.

Purpose of the Study:

• To investigate the binding of fd gene 5 protein (G5P) to double-stranded synthetic DNA polymers.
• To characterize the structural changes induced by G5P binding using circular dichroism (CD).
• To assess the effect of G5P on the thermal stability of these DNA polymers.

Main Methods:

• Circular dichroism (CD) spectroscopy was used to monitor spectral changes upon protein binding.
• Melting temperature (Tm) analysis was performed to quantify the effect of G5P on DNA stability.
• Experiments were conducted with different DNA polymer forms (double-stranded and single-stranded) and varying salt concentrations.

Main Results:

• CD data confirmed that G5P forms complexes with double-stranded poly(dA.dT) and poly[d(A-T).d(A-T)], with altered CD spectra above 255 nm.
• G5P binding caused a significant decrease (>65%) in the tyrosyl CD band, more pronounced than with single-stranded DNA but similar to double-stranded RNA.
• G5P binding reduced the melting temperature of poly(dA.dT); this destabilization effect was significantly influenced by binding to the double-stranded form and salt concentration.

Conclusions:

• fd gene 5 protein interacts with double-stranded synthetic DNA polymers, inducing distinct structural changes.
• G5P binding significantly destabilizes the DNA double helix, with the extent of destabilization dependent on the binding mode (single- vs. double-stranded) and ionic strength.
• The study provides insights into the biophysical mechanisms of G5P-nucleic acid interactions and their impact on DNA stability.