Analyzing protein posttranslational modifications using enzyme-catalyzed expressed protein ligation

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Chemistry

Background:

• Expressed protein ligation (EPL) is a method for site-specific protein modification.
• Traditional EPL requires a Cysteine residue at the ligation site, limiting its application.
• Posttranslational modifications (PTMs) are crucial for protein function and are often studied using modified proteins.

Purpose of the Study:

• To develop a novel method for expressed protein ligation that does not require a Cysteine residue.
• To expand the utility of EPL for incorporating complex modifications, such as multiple PTMs.
• To demonstrate the applicability of this new method for studying protein function.

Main Methods:

• Enzyme-catalyzed expressed protein ligation (EPL) using subtiligase.
• Generation of protein C-terminal thioesters and Cysteine-free peptides.
• Purification of the ligated protein product.

Main Results:

• Successfully ligated Cysteine-free peptides to protein thioesters using subtiligase.
• Demonstrated the incorporation of site-specific phosphorylations onto the C-terminal tail of PTEN.
• Obtained substantial yields of the modified protein for further analysis.

Conclusions:

• Enzyme-catalyzed EPL provides a versatile alternative to traditional EPL, overcoming the Cysteine limitation.
• This method enables the efficient generation of site-specifically modified proteins with complex PTMs.
• The developed technique is valuable for biochemical and biophysical studies of protein function and regulation.