Three-dimensional structure of clathrin cages in ice

Area of Science:

• Structural biology
• Biochemistry
• Cell biology

Background:

• Clathrin cages are protein structures essential for intracellular transport.
• Understanding their precise architecture is key to deciphering their function.

Purpose of the Study:

• To determine the three-dimensional structure of clathrin cages.
• To identify the structural components responsible for the inner shell formation.

Main Methods:

• Collected tilt series of electron micrographs from unstained clathrin cages.
• Generated three-dimensional reconstructions using cryo-electron microscopy.
• Examined different preparations including intact cages, reassembled cages, and cages treated with proteases (elastase, trypsin).

Main Results:

• Achieved high-resolution 3D reconstructions of individual hexagonal clathrin barrels.
• Identified an inner shell of material within intact and elastase-treated cages.
• Demonstrated that trypsin digestion removes this inner shell, indicating its composition.

Conclusions:

• The inner shell of clathrin cages is formed by the terminal domains of clathrin heavy chains.
• This finding provides detailed insights into the structural organization of clathrin cages.
• The study elucidates the role of specific clathrin domains in cage assembly and stability.