Polymorphic Protective Dps-DNA Co-Crystals by Cryo Electron Tomography and Small Angle X-Ray Scattering

Area of Science:

• Molecular Biology
• Structural Biology
• Biophysics

Background:

• Histone-like Dps protein plays a crucial role in protecting cellular DNA from damage.
• Intracellular crystallization of Dps protein with DNA is a significant but poorly understood phenomenon.
• The precise structure of Dps-DNA co-crystals has remained elusive for over 20 years.

Purpose of the Study:

• To elucidate the detailed three-dimensional structure of Dps-DNA co-crystals.
• To investigate the influence of buffer parameters on co-crystal formation and morphology.
• To characterize the different types of Dps-DNA co-crystals formed in vitro.

Main Methods:

• Cryo-electron tomography (cryo-ET) was employed to visualize co-crystal structures.
• Small-angle X-ray scattering (SAXS) was used to determine lattice parameters.
• Three-dimensional reconstruction techniques were applied to analyze cubic co-crystals.

Main Results:

• Dps-DNA co-crystals exhibit polymorphous modifications dependent on buffer conditions.
• Two distinct crystalline forms were identified in vitro: triclinic and cubic.
• The molecular arrangement of DNA and Dps proteins within cubic lattices was resolved, with consistent unit cell parameters determined by cryo-ET and SAXS.

Conclusions:

• The study provides the first detailed structural insights into Dps-DNA co-crystals.
• Buffer parameters significantly influence the formation of different Dps-DNA co-crystal polymorphs.
• The findings advance our understanding of genome protection mechanisms and in vitro crystallization processes.