Expression and characterization of human lamin C.

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Lamin C is a crucial intermediate filament protein involved in nuclear structure.
• Understanding lamin C assembly is vital for comprehending nuclear mechanics and disease.
• Previous expression systems faced challenges with fusion peptide removal.

Purpose of the Study:

• To express functional human lamin C in E. coli.
• To investigate the structural and assembly properties of expressed lamin C.
• To determine the role of the C-terminal non-helical domain in lamin C assembly.

Main Methods:

• Expression of human lamin C cDNA in E. coli using a modified pLcII vector system.
• Purification and characterization of expressed lamin C.
• Analysis of particle structure using shadowed preparations.
• Investigation of assembly properties through paracrystal formation.
• Site-specific mutagenesis to create a lamin C fragment lacking the C-terminal domain.

Main Results:

• Expressed lamin C exhibited structural characteristics and assembly properties similar to native lamin C, forming 50-nm rod-like particles and paracrystals with a 22.5 nm axial repeat.
• Isolated molecules showed a dimeric structure with two globular domains.
• A lamin C fragment lacking the C-terminal non-helical domain also formed paracrystals, indicating this domain is not essential for assembly.

Conclusions:

• The modified pLcII vector system is effective for expressing functional lamin C with retained structural and assembly properties.
• Human lamin C self-assembles into characteristic structures, demonstrating conserved assembly mechanisms.
• The C-terminal non-helical domain is not essential for the fundamental assembly of lamin C into higher-order structures.