Expressed protein ligation-mediated template protein extension

Area of Science:

• Biochemistry
• Protein Engineering
• Structural Biology

Background:

• Human apolipoprotein A-I (apoA-I) is crucial for lipid metabolism.
• Understanding apoA-I structure-function relationships is vital for disease research.
• Truncated apoA-I variants may exhibit altered biophysical properties.

Purpose of the Study:

• To investigate sequence requirements for apoA-I folding using expressed protein ligation (EPL).
• To assess if extending a truncated apoA-I variant enhances its secondary structure and stability.
• To develop a general protein engineering strategy for modifying recombinant polypeptide length.

Main Methods:

• Expressed protein ligation (EPL) was employed to ligate a synthetic peptide to a C-terminal truncated apoA-I (residues 1-172).
• Expressed apoA-I(1-172) was isolated from Escherichia coli.
• Biophysical properties, including secondary structure and stability, were compared before and after EPL.

Main Results:

• ApoA-I(1-172) showed reduced α-helix content and lower stability compared to full-length apoA-I.
• EPL successfully created apoA-I(Milano)(1-192) by adding 20 residues to apoA-I(1-172).
• The EPL product, apoA-I(Milano)(1-192), exhibited biophysical properties similar to full-length apoA-I(Milano).

Conclusions:

• Extending the truncated apoA-I variant via EPL confers improved secondary structure and stability.
• EPL provides a versatile and cost-effective method for protein engineering and structure-function studies.
• This strategy facilitates the investigation of apolipoprotein fragments and domains of varying sizes.