Recombinant proteins
Protein is an important component of all organisms. Each protein molecule consists of one or more polypeptide chains made of amino acids. There are 20 naturally occurring amino acids. Different series of amino acids are linked together by peptide bonds to form protein chains. Each protein has a unique sequence of amino acids. All the functions of proteins are dependent on their structures. Although information necessary for life is encoded by DNA or RNA, proteins perform a wide range of biological functions within organisms, including enzyme catalysis, defense, transport, support, motion, and regulation. According to their functions in the body, proteins can be divided into different categories, such as antibody, enzyme, messager, structural component, and transport/ storage protein. Given the important functions of proteins, proteins have been studied intensively and applied widely.
In the past, the major way to obtain a specific protein was to isolate it from a natural source, which is generally inefficient and time-consuming. Recent advances in recombinant molecule biological techniques have made it possible to clone the DNA encoding a specific protein into an expression vector and express the protein in expression systems, such as bacteria, yeast, insect cells, and mammalian cells. Simply put, recombinant proteins are translated products of exogenous DNA in living cells. The production of recombinant proteins generally contains two major steps: molecule cloning and protein expression. Currently, recombinant protein production is one of the most powerful techniques used in life sciences. Recombinant proteins have wide applications in medicine, research, and biotechnology.
1. Medicine
Therapeutic proteins provide important therapies for a variety of diseases, such as diabetes, cancer, infectious diseases, hemophilia, and anemia. Common therapeutic proteins include antibodies, FC fusion proteins, hormones, interleukins, enzymes, and anticoagulants. There is a growing demand for recombinant proteins for therapeutic applications. Human proteins obtained through genetic engineering play a key role in therapeutic medicines market. Currently, most of all recombinant therapeutic proteins are produced in mammalian cells because mammalian cells are capable of producing high-quality proteins similar to the naturally occurring ones. In addition, many approved recombinant therapeutic proteins are generated in Escherichia coli due to its well-characterized genetics, rapid growth, and high-yield production.
Basically, therapeutic proteins can be classified into four groups.
Group I: Therapeutic proteins with enzymatic or regulatory activity. These proteins replace a protein that is deficient or abnormal, up-regulate an existing pathway, or provide a new function or activity.
Group II: Therapeutic proteins with special targeting activity. These proteins interfere with a molecule or organism or deliver other molecules.
Group III: Therapeutic proteins as vaccines. These proteins help protect against foreign agents, autoimmune diseases, and cancer.
Group IV: Therapeutic proteins as diagnostics. These proteins are generally purified and recombinant proteins.
2. Research
Recombinant proteins help to elucidate the basic and fundamental principles of an organism. These molecules can be used to identify and locate the position of the protein encoded by a specific gene, and to uncover the function of other genes in various cellular activities such as cell signaling, metabolism, growth, replication and death, transcription, translation, and protein modification. Thus, recombinant proteins are frequently used in molecular biology, cell biology, biochemistry, structural and biophysical studies, and many other research fields.
Recombinant proteins are useful tools in understanding protein-protein interactions. They have proven performance in several laboratory techniques, such as ELISA, Western Blot, and immunohistochemistry (IHC). Recombinant proteins can be used to develop enzymatic assays. When used in conjunction with a matched antibody pair, recombinant proteins can be used as standards such as ELISA standards. Moreover, recombinant proteins can be used as positive controls in Western blots.
3. Biotechnology
Recombinant proteins are also used in industry, food production, agriculture, and bioengineering. For example, in breeding industry, enzymes can be added to animal feed to increase the nutritional value of feed ingredients, reduce feed and waste management costs, support animal gut health, enhance animal performance and improve the environment. Besides, lactic acid bacteria (LAB) have been used for a long time for the production of fermented foods, and recently, LAB has been engineered for the expression of recombinant proteins, which have wide applications such as improving human/animal digestion and nutrition.