Rational Redesign of a Functional Protein Kinase-Substrate Interaction

Area of Science:

• Molecular Biology
• Cell Signaling
• Synthetic Biology

Background:

• Protein kinases are crucial for cell signaling, phosphorylating substrates at specific sequence motifs.
• Kinase-substrate recognition relies on precise interactions within the active site.
• Developing orthogonal signaling systems requires modifying kinase specificity.

Purpose of the Study:

• To re-engineer the protein kinase Pim1 to alter its phosphorylation consensus sequence.
• To create an orthogonal kinase-substrate pair for novel signaling applications.
• To demonstrate the utility of engineered kinases in cellular protection against apoptosis.

Main Methods:

• Mutagenesis of the protein kinase Pim1 catalytic domain to alter substrate recognition.
• Introduction of a compensating mutation in the Pim1 substrate, protein BAD.
• In vitro and in vivo phosphorylation assays to validate the engineered pair.
• Coexpression of the engineered kinase-substrate pair in cells to assess functional outcomes.

Main Results:

• A modified Pim1 kinase mutant was created that recognizes a hydrophobic residue instead of arginine.
• The engineered kinase successfully phosphorylated the mutated BAD substrate in vitro and in living cells.
• Coexpression of the orthogonal pair conferred protection against apoptosis in cells.
• Demonstrated the feasibility of orthogonal kinase-substrate interactions for synthetic signaling.

Conclusions:

• Engineered protein kinases can be used to create specific, orthogonal signaling pathways.
• Orthogonal kinase-substrate pairs serve as valuable tools for studying phosphorylation events in cells.
• This approach enables the design of synthetic signaling systems with tailored functions, such as apoptosis resistance.