Cryo-EM Analyses Permit Visualization of Structural Polymorphism of Biological Macromolecules

Area of Science:

• Structural biology
• Biophysics
• Biochemistry

Background:

• Biological macromolecule function is linked to structural polymorphism, where identical molecules adopt different conformations.
• Traditional X-ray crystallography, while accurate, is limited by crystal packing artifacts, hindering the study of molecules in solution.
• A need exists for methods that can analyze macromolecular structures in their native, solution-state environment.

Purpose of the Study:

• To review the application of cryo-electron microscopy (cryo-EM) in studying structural polymorphism of macromolecules in solution.
• To highlight recent advancements in cryo-EM and computational analysis for revealing protein conformational dynamics.
• To discuss the potential of cryo-EM for RNA structural polymorphism analysis.

Main Methods:

• Single-particle cryo-electron microscopy (cryo-EM) for determining macromolecular structures in solution.
• Three-dimensional (3D) classification algorithms, including neural network and deep learning approaches, to analyze heterogeneous structural data.
• Analysis of cryo-EM data to capture and resolve co-existing conformational states.

Main Results:

• Cryo-EM enables routine determination of macromolecular structures in solution at resolutions comparable to crystallography.
• Cryo-EM data capture rich information on structural polymorphism, revealing insights into allostery, subunit cooperativity, and functional plasticity in proteins.
• Advancements in 3D classification algorithms are crucial for disentangling complex structural ensembles.

Conclusions:

• Cryo-EM is a powerful alternative to crystallography for studying structural polymorphism and its functional implications in macromolecules.
• Emerging cryo-EM techniques are poised to significantly advance the study of RNA structural polymorphism.
• The ability to study molecules in solution provides a more biologically relevant understanding of conformational dynamics.