Metallothionein as a clonable high-density marker for cryo-electron microscopy

Area of Science:

• Structural Biology
• Cell Biology
• Biophysics

Background:

• Cryo-electron microscopy (cryo-EM) is advancing to image larger cellular structures.
• Identifying components in complex cellular specimens is challenging due to numerous biomolecules.
• Current labeling methods for cryo-sections are limited as treatments must occur before freezing.

Purpose of the Study:

• To introduce metallothionein (MTH) as a novel, clonable label for cryo-EM.
• To enable high-resolution identification of cellular structures in vitrified specimens.
• To demonstrate MTH's utility in labeling protein filaments.

Main Methods:

• Engineered metallothionein (MTH) as a metal-clustering protein label.
• Applied MTH to label kinesin-decorated microtubules (MTs).
• Applied MTH to label desmin intermediate filament (IF) building blocks.
• Utilized cryo-electron microscopy for high-resolution imaging.

Main Results:

• MTH successfully clustered metal atoms into high-density particles.
• Achieved high spatial resolution in labeling MTs and IFs.
• Demonstrated MTH's effectiveness as a pre-freezing label for cellular components.

Conclusions:

• Metallothionein (MTH) is a viable and effective label for cryo-EM of cellular structures.
• MTH facilitates unambiguous identification of components within complex biological specimens.
• This labeling strategy enhances the resolution and scope of cryo-electron microscopy.