Subunit conformational variation within individual GroEL oligomers resolved by Cryo-EM

Area of Science:

• Structural Biology
• Biochemistry
• Microscopy Techniques

Background:

• Single-particle cryo-electron microscopy (cryo-EM) is advancing the study of heterogeneous molecular structures.
• Existing cryo-EM methods typically average identical conformations, potentially masking dynamic variations within oligomers.

Purpose of the Study:

• To investigate conformational heterogeneity among chemically identical subunits within a single GroEL oligomer using cryo-EM.
• To analyze the distribution and correlation of different subunit conformations within the oligomer.

Main Methods:

• Utilized a 3.5-Å cryo-EM reconstruction with imposed D7 symmetry for detailed analysis.
• Applied focused classification to the 14 subunits of the GroEL oligomer to identify distinct conformational states.
• Mapped and analyzed the spatial distribution of identified subunit conformations within the oligomer.

Main Results:

• Identified three dominant classes of subunit conformations, each resembling known GroEL crystal structures.
• Conformational differences were primarily attributed to variations in apical domain orientation.
• Observed non-random spatial distributions of conformations, with adjacent subunits showing a higher likelihood of similar conformations.

Conclusions:

• Demonstrates the capability of cryo-EM to resolve structural dynamics within a single protein oligomer.
• Suggests correlated conformational states among adjacent subunits in the GroEL oligomer.
• Highlights the potential of advanced cryo-EM analysis for understanding protein functional dynamics.