Improving the diffraction of apoA-IV crystals through extreme dehydration

Area of Science:

• Structural Biology
• Protein Crystallography
• Biochemistry

Background:

• Apolipoproteins, protein components of high-density lipoproteins (HDL), are crucial for lipid transport.
• Apolipoprotein self-association complicates protein crystallization.
• The core fragment of apolipoprotein A-IV (apoA-IV) was investigated for crystallization.

Purpose of the Study:

• To present the crystallization and diffraction of apoA-IV(64-335).
• To explore methods for improving diffraction quality of apoA-IV crystals.

Main Methods:

• Crystallization of apoA-IV(64-335) in hexagonal (P6) morphologies.
• Preliminary X-ray diffraction experiments.
• Application of crystal dehydration techniques with varying PEG 3350 concentrations and durations.
• Assessment of crystal quality based on dehydration tolerance.

Main Results:

• ApoA-IV(64-335) crystallized readily, exhibiting hexagonal morphologies with a long axis of ~550 Å.
• Initial diffraction was limited to 3.5 Å resolution.
• Crystal dehydration significantly improved diffraction quality.
• One crystal morphology withstood extreme dehydration (60% PEG 3350 for >12 h), yielding diffraction to 2.7 Å resolution.

Conclusions:

• Crystal dehydration is an effective method for enhancing apoA-IV crystal diffraction.
• Integrating dehydration with varied crystal growth conditions may be a general strategy for optimizing protein diffraction resolution.