Cell-free N-terminal protein labeling using initiator suppressor tRNA

Area of Science:

• Biochemistry
• Molecular Biology
• Synthetic Biology

Background:

• Cell-free protein synthesis offers advantages for producing modified proteins.
• Site-specific labeling is crucial for studying protein structure and function.
• Existing methods for N-terminal labeling can be inefficient or lack specificity.

Purpose of the Study:

• To develop a highly efficient method for introducing fluorophores and other markers at the N terminus of proteins.
• To enable site-specific protein labeling in a cell-free expression system.
• To demonstrate the utility of this method for biophysical and biotechnological applications.

Main Methods:

• Utilized an amber (CUA) initiator suppressor tRNA aminoacylated with a fluorophore-amino acid conjugate.
• Introduced the modified tRNA into an Escherichia coli S30 cell-free translation system.
• Employed a DNA template with an amber (UAG) codon instead of the standard initiation (AUG) codon.

Main Results:

• Successfully incorporated the fluorophore BODIPY-F1 at the N terminus of several model proteins.
• Achieved specific labeling efficiencies ranging from 27% to 67%.
• Demonstrated significantly higher specific labeling compared to wild-type tRNAs.

Conclusions:

• The developed method provides an efficient and specific way to achieve N-terminal protein labeling in cell-free extracts.
• This technology has broad potential for applications in biophysics and biotechnology.
• The approach facilitates the production of precisely labeled proteins for various research purposes.