Effects of ssDNA sequences on non-sequence-specific protein binding

Area of Science:

• Biochemistry
• Molecular Biology
• Spectroscopy

Background:

• Single-stranded DNA (ssDNA) structure is influenced by nucleotide sequence.
• ssDNA binding proteins significantly alter ssDNA conformation and spectra.
• Proteins like Ff bacteriophage gene 5 protein (g5p) and RPA70-A share structural similarities but have distinct spectra.

Purpose of the Study:

• To investigate how g5p and RPA70-A binding affects ssDNA circular dichroism (CD) spectra.
• To determine if nearest-neighbor interactions in ssDNA are conserved upon protein binding.
• To compare the spectral properties of g5p and RPA70-A and their impact on ssDNA.

Main Methods:

• Circular dichroism (CD) spectroscopy was used to analyze ssDNA and protein-ssDNA complexes.
• Analysis of CD spectra for various ssDNA sequences, including repetitive A and C combinations.
• Application of nearest-neighbor equations to ssDNA spectra before and after protein binding.

Main Results:

• Both g5p and RPA70-A binding similarly perturb ssDNA CD spectra, despite differences in their own spectra.
• Nearest-neighbor interactions in ssDNA are maintained within the protein binding sites.
• Nearest-neighbor equations accurately describe the CD spectra of protein-bound ssDNAs.

Conclusions:

• The binding sites of g5p and RPA70-A impose a similar average structure on ssDNA nearest neighbors.
• Nearest-neighbor analysis remains a valid approach for studying protein-bound ssDNA structure.
• CD spectroscopy is a powerful tool for characterizing protein-ssDNA interactions.