Intrinsic protein disorder could be overlooked in cocrystallization conditions: An SRCD case study

Area of Science:

• Structural biology
• Biochemistry
• Protein science

Background:

• X-ray diffractometry is a primary method for determining 3D protein structures.
• Protein structures can be partially or fully disordered in their native state.
• Understanding protein structure is crucial for drug design and molecular biology.

Purpose of the Study:

• To investigate whether cocrystallization conditions can induce protein folds.
• To examine the structural consequences of protein modifications.
• To highlight the importance of studying intrinsically disordered proteins in solution.

Main Methods:

• X-ray diffractometry for 3D structure determination.
• Synchrotron radiation circular dichroism spectroscopy for solution structure analysis.
• Cocrystallization techniques.

Main Results:

• Cocrystallization conditions can lead to induced protein folds, masking original structures.
• The Im7 immunity protein was shown to stabilize the native-like solution structure of unfolded NColE7 nuclease mutants through complex formation.
• Crystal structures of NColE7 with its inhibitor or substrate were nearly identical, suggesting stabilization of a specific fold.

Conclusions:

• Protein structures determined by X-ray crystallography under cocrystallization may not represent the native state.
• Intermolecular interactions can mask the structural consequences of protein modifications.
• Complementary solution-phase experiments are essential for studying intrinsically disordered proteins.