Diffraction-quality, ultraflexible protein single crystals engineered with DNA

Area of Science:

• Biomolecular engineering
• Nanomaterials science
• Structural biology

Background:

• DNA-functionalized nanoparticles typically exhibit limited atomic-level order due to flexible DNA interactions.
• Achieving ordered crystalline structures with flexible components presents a significant challenge in materials science.

Purpose of the Study:

• To develop a valence-centric strategy for creating DNA-bonded protein single crystals with tunable mechanical properties.
• To investigate the role of DNA hybridization in protein crystallization and its impact on structural order and mechanical behavior.

Main Methods:

• Site- and number-selective conjugation of an octameric enzyme (glutarate L-2-hydroxylase) with eight DNA strands to form octavalent molecular bonds.
• Assembly of the DNA-protein conjugates into body-centered tetragonal crystals.
• X-ray diffraction analysis to determine crystal structure and resolution (1.42–2.61 angstroms).
• Mechanistic studies to elucidate the role of DNA dynamics in crystallization.

Main Results:

• Successfully assembled DNA-protein conjugates into ordered body-centered tetragonal crystals with DNA helices mediating contacts.
• Demonstrated that increasing oligonucleotide length causes anisotropic lattice expansion while maintaining atomic periodicity.
• Observed that DNA-hybridized crystals are 23-fold softer than native protein crystals.
• Mechanistic studies indicated dynamic motion of unhybridized DNA aids crystallization.

Conclusions:

• Established a programmable framework for biomolecular crystallization and nanomaterials engineering with atomic precision.
• Challenged the assumption that flexibility is incompatible with structural order in crystalline materials.
• Developed protein crystals with unconventional, significantly enhanced mechanical softness through DNA hybridization.