Protein Engineering: Strategies for Enzyme Optimization

Protein Engineering and Strategies to Improve Enzymes

With roots in recombinant DNA technology, the field of protein engineering regards gene modifications as changes to protein sequences that bestow desired properties. Protein engineering is considered the next big step after genetic engineering. Many methods of precisely constructing proteins may be broadly categorized as methods requiring substantial previous protein interaction, hence introducing the concept of a methodical directed evolution approach that promotes the expression of the natural evolutionary process. One may employ rational design, non-rational design, or both.

There are several applications for the emerging field of protein engineering in research, industry, pharmaceutics, trade, and laundry. Protein engineering has made it feasible to create novel proteins with the goal of diagnosing, treating, and improving health. Proteases and amylases are two instances of altered enzyme classes with significant uses in the food, soap, paper, and other industries. Protein engineering can create intricate, stimulus-responsive pharmacological systems that alter the metabolic drug landscapes. Even though protein engineering treatment is still a relatively new field, current developments are being used to directly influence pharmacodynamics. This article provides an analysis of existing approaches and tactics for altering proteins at various levels, along with information on possible applications in nanobiotechnology, the food sector, and medicine.

Keywords: protein engineering, nanobiotechnology, recombinant DNA technology, industrial applications, therapeutic enzymes, therapeutic applications

Protein Engineering Techniques

Directed Evolution of Protein Catalysts

In directed evolution, several mutant copies of a gene are produced via targeted or random mutagenesis or computational methods, and these altered copies are then employed to build related proteins. As a result, a library of various proteins is produced, and those with the appropriate qualities are carefully tested and selected. This approach is similar to evolution, where natural selection has developed a wide range of large protein families throughout time. While this method is laborious and time-consuming, it focuses on a limited number of protein alterations.

Strategies to Improve Protein and Enzyme Properties

The main methods of protein engineering are rational design and directed evolution. These strategies are often used together.

• Rational Design: Scientists use their knowledge of a protein's structure and function to make specific changes, often by altering the DNA sequence to produce a particular amino acid substitution.
  • Techniques: Site-directed mutagenesis is a key technique to introduce specific point mutations, insertions, or deletions.
  • Basis: This method relies on having a detailed understanding of the protein's 3D structure and how mutations affect its activity.
• Directed Evolution: This process iteratively mimics natural selection in a lab setting.
  • Mutagenesis: A library of protein variants is created through random mutations.
  • Selection: Variants with the desired trait are identified from the library.
  • Amplification: The genes of the successful variants are amplified to create the starting material for the next round.
  • Advantage: This method is useful when the relationship between a protein's sequence and function is not fully understood.

Maxam-Gilbert Method of DNA Sequencing

Allan Maxam and Walter Gilbert published a DNA sequencing method in 1977 based on chemical modification of DNA and subsequent cleavage at specific bases. Also known as chemical sequencing, this method allowed purified samples of double-stranded DNA to be used without further cloning. This method's use of radioactive labeling and its technical complexity discouraged extensive use after refinements in the Sanger methods had been made.

Maxam-Gilbert sequencing requires radioactive labeling at one 5' end of the DNA and purification of the DNA fragment to be sequenced. Chemical treatment then generates breaks at a small proportion of one or two of the four nucleotide bases in each of four reactions (G, A+G, C, C+T). The concentration of the modifying chemicals is controlled to introduce on average one modification per DNA molecule. Thus, a series of labeled fragments is generated, from the radiolabeled end to the first "cut" site in each molecule. The fragments in the four reactions are electrophoresed side by side in denaturing acrylamide gels for size separation. To visualize the fragments, the gel is exposed to X-ray film for autoradiography, yielding a series of dark bands each corresponding to a radiolabeled DNA fragment, from which the sequence may be inferred.

Principle of Chemical Sequencing

The first DNA sequencing technique, using chemical reagents, was developed by Maxam and Gilbert (1977). The method is described as follows:

1. A strand of source DNA is labeled at one end with 32P.
2. The two strands of DNA are then separated.
3. The labeled DNA is distributed into four samples in separate tubes.
4. Each sample is subjected to treatment with a chemical that specifically destroys one (G, C) or two bases (A + G, T + C) in the DNA.
5. This results in the formation of a series of labeled fragments of varying lengths.

The actual length of the fragment depends on the site at which the base is destroyed from the labeled end. Thus, for instance, if there are C residues at positions 4, 7, and 10 away from the labeled end, then the treatment of DNA that specifically destroys C will give labeled pieces of length 3, 6, and 9 bases. The labeled DNA fragments obtained in the four tubes are subjected to electrophoresis side by side and they are detected by autoradiograph. The sequence of the bases in the DNA can be constructed from the bands on the electrophoresis.