Using single-molecule approaches to study archaeal DNA-binding protein Alba1

Area of Science:

• Microbiology
• Molecular Biology
• Biophysics

Background:

• Thermophilic and hyperthermophilic archaea possess Alba genes encoding Alba proteins.
• Alba proteins are dimeric, basic proteins that bind DNA cooperatively.
• The precise functions and DNA interaction mechanisms of Alba proteins are not fully understood.

Purpose of the Study:

• To investigate the DNA-binding properties and interactions of Alba1 protein from thermophilic archaea.
• To elucidate the structural and functional consequences of Alba1 binding to DNA.

Main Methods:

• Single-molecule tethered particle motion (TPM) experiments.
• Optical tweezers (OT) measurements.
• Incoming-strand TPM experiments to study Alba1 nucleoprotein filament interactions.

Main Results:

• Alba1 binding to double-stranded DNA increases Brownian motion amplitude, indicating cooperative binding.
• Optical tweezers revealed a 5-fold increase in DNA persistence length due to Alba1 binding, with minimal change in contour length.
• Alba1 binding is DNA length-dependent, suggesting more initiation sites on longer DNA molecules.
• Significant dimer-dimer contacts between Alba1 nucleoprotein filaments were observed, regulated by Alba1 concentration.

Conclusions:

• Alba1 binding significantly alters DNA structure by increasing its stiffness (persistence length).
• The cooperative binding and DNA length dependence suggest a role in DNA organization or protection in archaea.
• Alba1 nucleoprotein filaments exhibit self-interaction, regulated by protein concentration, potentially influencing higher-order DNA structures.