Structural analysis of interdomain mobility in ribosomal L1 proteins

Area of Science:

• Structural biology
• Molecular biology
• Biochemistry

Background:

• Ribosomal protein L1 (RL1) has two domains linked by polypeptide fragments, influencing its open or closed conformation.
• Archaea RL1 exhibits an open conformation, while bacteria RL1 shows a closed conformation when unbound to RNA.

Purpose of the Study:

• To investigate the structural basis for the conformational differences between archaeal and bacterial ribosomal protein L1.
• To determine if a specific amino acid difference accounts for the closed conformation in bacterial RL1.

Main Methods:

• Comparative analysis of L1 amino acid sequences from archaea and bacteria.
• Site-directed mutagenesis to create a bacterial RL1 mutant lacking a specific residue.
• X-ray crystallography to solve the crystal structure of the mutant Thermus thermophilus L1.

Main Results:

• Bacterial RL1 proteins possess an extra residue in an interdomain fragment compared to archaeal RL1.
• A Thermus thermophilus L1 mutant lacking this extra residue adopted an open conformation.
• The mutation successfully converted the closed bacterial RL1 conformation to an open one, mimicking archaeal RL1.

Conclusions:

• A single amino acid difference in the interdomain hinge region is responsible for the distinct closed conformation of bacterial ribosomal protein L1.
• This finding provides insight into the structural evolution and conformational flexibility of ribosomal proteins.