In News:

• Scientists from ETH Zurich and the Technical University of Munich have developed a novel method to engineer bacteria to produce customised “designer proteins” using artificial amino acids.
• The breakthrough enables microorganisms to synthesize proteins with new biological and chemical properties, opening possibilities for advanced drug delivery systems and next-generation biotechnology applications.
• The research focuses on modifying nutrient transport mechanisms in bacteria such as Escherichia coli (E. coli) so that cells can efficiently import artificial amino acids required to build synthetic proteins.

Nutrient Transporter Proteins

• A nutrient transporter protein is a membrane-bound protein that facilitates the movement of essential molecules such as amino acids, peptides, and other nutrients—across the cell membrane.
• In the recent research, scientists engineered a specialized ABC (ATP-Binding Cassette) transporter in bacteria. Normally, this transporter imports small peptide molecules used as nutrients. By modifying it, researchers enabled bacterial cells to import peptides carrying artificial amino acids, which can then be used to assemble customised proteins.

Objective of the Research

• The main goal of the study was to enable cells to incorporate artificial amino acids into proteins efficiently. Natural proteins are typically built from 20 standard amino acids, but introducing synthetic amino acids allows scientists to design proteins with new functional properties.
• However, artificial amino acids generally cannot easily cross the cell membrane. By engineering a transporter protein capable of importing these molecules, researchers overcame a major barrier in synthetic biology and protein engineering.

Mechanism of the System

The engineered system works through a multi-step biological process:

1. Engineering of ABC Transporter – Scientists modified the transporter protein to improve its ability to import peptides containing artificial amino acids.
2. Trojan Horse Strategy – Artificial amino acids are concealed inside short peptide chains such as tripeptides or tetrapeptides composed of natural amino acids.
3. Transport into the Cell – The transporter imports these peptide chains across the cell membrane.
4. Release of Artificial Amino Acids – Once inside the cell, enzymes break the peptides into individual amino acids.
5. Protein Synthesis – The ribosome, the cellular machinery responsible for protein production, incorporates the artificial amino acids into newly synthesized proteins.

Through this approach, bacterial cells can generate custom-designed proteins on demand.

Key Innovations

• Trojan Horse Delivery Strategy: Artificial amino acids are hidden within natural peptide structures, allowing them to bypass cellular membrane barriers and enter the cell.
• Engineered ABC Transporter: The modified transporter is capable of importing up to ten times more artificial amino acids compared to natural transport systems.
• Directed Evolution: Researchers used directed evolution, a technique that mimics natural selection in the laboratory, to improve the efficiency of the transporter protein under nutrient-rich conditions.
• Multifunctional Protein Design: The system allows two different artificial amino acids to be incorporated into a single protein, enabling complex and multifunctional molecular designs.
• Compatibility with Standard Laboratory Conditions: The engineered bacteria can function effectively in standard laboratory growth media, making the system practical for widespread scientific use.