An extended DNA structure through deoxyribose-base stacking induced by RecA protein

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• RecA proteins are essential for homologous genetic recombination across diverse organisms.
• RecA proteins form helical filaments with single-stranded DNA (ssDNA) in the presence of ATP.
• ssDNA within RecA filaments is extended, facilitating homologous pairing with double-stranded DNA.

Purpose of the Study:

• To determine the three-dimensional structure of single-stranded DNA bound to RecA protein.
• To elucidate the structural basis for DNA extension within RecA filaments.
• To understand the role of this structural change in homologous pairing.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
• The study focused on the RecA-ssDNA complex.

Main Results:

• A novel deoxyribose-base stacking was identified in the ssDNA bound to RecA protein.
• The 2'-methylene of deoxyribose stacks on the base of the next residue, deviating from normal base stacking.
• This novel stacking results in bases being spaced approximately 5 Å apart, causing axial DNA extension.

Conclusions:

• The determined structure explains the axial extension of DNA within RecA filaments compared to B-form DNA.
• This structural insight provides a mechanistic understanding of how RecA facilitates homologous pairing during genetic recombination.