A Three-protein Charge Zipper Stabilizes a Complex Modulating Bacterial Gene Silencing.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Nucleoid-associated proteins (NAPs) like Hha/YmoA play a role in gene silencing.
• Horizontally acquired genetic material, including virulence and antibiotic resistance genes, requires maintenance.
• Hha family proteins modulate the selectivity of H-NS binding.

Purpose of the Study:

• To elucidate the structural basis of selective binding between Hha/YmoA and H-NS.
• To investigate the dynamics of YmoA and its relationship with H-NS binding.
• To understand the role of electrostatic interactions in protein complex formation.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy
• NMR relaxation dispersion experiments
• Structural modeling
• Site-directed mutagenesis

Main Results:

• A three-protein charge zipper model explains the selective interaction between Hha/YmoA and the H-NS dimer.
• YmoA exhibits microsecond-millisecond dynamics in its free form, dependent on salt concentration.
• H-NS binding influences YmoA dynamics, and a D43N mutation disrupts both binding and dynamics.

Conclusions:

• The selective binding of Hha/YmoA to H-NS is mediated by a charge zipper mechanism.
• YmoA dynamics are functionally linked to its interaction with H-NS.
• These findings provide insights into the regulation of horizontally acquired genes.