Biochemists are excited by the possibilities presented by peptides and proteins as pharmaceuticals because they so often mimic exactly the behaviour of a natural ligand — the substance that interacts with the receptor on an enzyme or cell to cause a biological process. This gives peptide drugs the potential to be more precisely targeted, with fewer side effects than small-molecule drugs. Within the body, there are lot of different hormones that react with cells and trigger different biological processes.
Often these are peptides, either cyclic versions or straight, linear ones. There are also manufacturing considerations that make peptides attractive — their length allows them to be chemically synthesised, as opposed to proteins that are generally expressed in yeast or mammalian cells. The most promising application of proteins is as antibodies , which are themselves a form of protein.
Particularly in anti-cancer applications, there are a lot of antibodies either in the clinic or under development. Two well-known examples are Herceptin trastuzumab for breast cancer, and Humira adalimumab for rheumatoid arthritis and other autoimmune diseases. In the case of antibodies, protein-based drugs use the same strategy as the body does to target things.
That way the drug can provide the specificity required, while also avoiding the off-target effects that a small molecule drug can have, causing bad side effects. Stability can be an issue, as peptides can degrade very quickly, and that means it can be difficult to dose a patient with a peptide. And according to your body, peptides and proteins are basically just food, which makes administering peptide drugs in an oral form quite difficult, as the body promptly digests them.
The pharmaceutical industry remains sceptical, mainly due to the stability issue, but also the difficulty in getting orally administered peptides to cross the barrier of the gut and be taken up by the bloodstream. But intravenous and subcutaneous use of peptides as drugs is becoming more common. There are around 60 FDA-approved peptide drugs on the market, with about peptide drugs in clinical trials, and over in pre-clinical before human testing development.
The sequence of amino acids in the chain determines how the chain will fold up to make the protein, so different proteins have different three-dimensional shapes. The three-dimensional shape of a protein determines its function. This is because proteins form attachments and interact with many other molecules and structures inside organisms. The shape of a protein determines what it can interact with, just like the shape of a key determines which locks it can operate. Most of the proteins in your body can be grouped into four categories based on the function they carry out.
Protein structure and variety Proteins are composed of chains of amino acids. National 5 Subjects National 5 Subjects up.
Molecules of a second chaperone, GroES, then form a lid over the chamber. Eukaryotes use different families of chaperone proteins, although they function in similar ways.
Chaperone proteins are abundant in cells. These chaperones use energy from ATP to bind and release polypeptides as they go through the folding process. Chaperones also assist in the refolding of proteins in cells.
Folded proteins are actually fragile structures, which can easily denature, or unfold. Although many thousands of bonds hold proteins together, most of the bonds are noncovalent and fairly weak. Even under normal circumstances, a portion of all cellular proteins are unfolded. Increasing body temperature by only a few degrees can significantly increase the rate of unfolding. When this happens, repairing existing proteins using chaperones is much more efficient than synthesizing new ones.
Interestingly, cells synthesize additional chaperone proteins in response to "heat shock. All proteins bind to other molecules in order to complete their tasks, and the precise function of a protein depends on the way its exposed surfaces interact with those molecules.
Proteins with related shapes tend to interact with certain molecules in similar ways, and these proteins are therefore considered a protein family. The proteins within a particular family tend to perform similar functions within the cell.
Proteins from the same family also often have long stretches of similar amino acid sequences within their primary structure. These stretches have been conserved through evolution and are vital to the catalytic function of the protein.
For example, cell receptor proteins contain different amino acid sequences at their binding sites, which receive chemical signals from outside the cell, but they are more similar in amino acid sequences that interact with common intracellular signaling proteins.
Protein families may have many members, and they likely evolved from ancient gene duplications. These duplications led to modifications of protein functions and expanded the functional repertoire of organisms over time. This page appears in the following eBook. Aa Aa Aa. Protein Structure. What Are Proteins Made Of? Figure 1: The relationship between amino acid side chains and protein conformation.
The defining feature of an amino acid is its side chain at top, blue circle; below, all colored circles. Figure 2: The structure of the protein bacteriorhodopsin. Bacteriorhodopsin is a membrane protein in bacteria that acts as a proton pump.
What Are Protein Families? Proteins are built as chains of amino acids, which then fold into unique three-dimensional shapes. Bonding within protein molecules helps stabilize their structure, and the final folded forms of proteins are well-adapted for their functions. Cell Biology for Seminars, Unit 2. Topic rooms within Cell Biology Close. No topic rooms are there.
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