Cryo-EM of dynamic protein complexes in eukaryotic DNA replication

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Eukaryotic DNA replication involves numerous dynamic protein interactions.
• Transient protein associations challenge traditional structural determination methods.
• Advancements in cryo-electron microscopy (cryo-EM) enable visualization of large protein complexes.

Purpose of the Study:

• To explore cryo-EM applications for studying weakly interacting protein complexes in eukaryotic DNA replication.
• To demonstrate methods for identifying components within low-resolution cryo-EM structures.
• To present a decade of cryo-EM studies on eukaryotic DNA replication machinery.

Main Methods:

• Direct mixing of purified proteins followed by 2D and 3D image sorting.
• Utilizing direct electron detectors and advanced image analysis algorithms for cryo-EM.
• Systematic fusion or insertion of maltose binding protein (MBP) for feature identification.

Main Results:

• Cryo-EM successfully captured and analyzed weakly interacting protein complexes.
• Low-resolution 2D averages provided significant biological insights into flexible complexes.
• MBP tagging proved effective for identifying specific proteins within complex structures.

Conclusions:

• Cryo-EM, combined with innovative sample preparation and analysis, can elucidate structures of transient protein assemblies.
• MBP tagging is a valuable strategy for characterizing components in low-resolution cryo-EM data.
• The described methodologies offer a framework for structural studies of other dynamic biological systems.