Protein folding is a process by which a polypeptide chain folds to become a biologically active protein in its native 3D structure. Protein structure is crucial to its function. Folded proteins are held together by various molecular interactions. Show
During translation, each protein is synthesized as a linear chain of amino acids or a random coil which does not have a stable 3D structure. The amino acids in the chain eventually interact with each other to form a well-defined, folded protein. The amino acid sequence of a protein determines its 3D structure. Folding of proteins into their correct native structure is key to their function. Failure to fold properly produces inactive or toxic proteins that malfunction and cause a number of diseases. Four stages of protein foldingThe folding of a protein is a complex process, involving four stages, that gives rise to various 3D protein structures essential for diverse functions in the human body. The structure of a protein is hierarchically arranged, from a primary to quaternary structure. The wide variation in amino acid sequences accounts for the different conformations in protein structure.
Factors affecting protein foldingProtein folding is a very sensitive process that is influenced by several external factors including electric and magnetic fields, temperature, pH, chemicals, space limitation and molecular crowding. These factors influence the ability of proteins to fold into their correct functional forms. Extreme temperatures affect the stability of proteins and cause them to unfold or denature. Similarly, extreme pH, mechanical forces and chemical denaturants can denature proteins. During denaturation, proteins lose their tertiary and secondary structures and become a random coil. Although denaturation is not always reversible, some proteins can re-fold under certain conditions. Some cells contain heat shock proteins or chaperones that protect proteins in the cell against heat denaturation. Chaperones help proteins to fold and remain folded under extreme temperatures. They also assist misfolded proteins in unfolding and re-folding correctly. Diseases related to incorrect protein foldingMisfolded proteins denature easily and lose their structure and function. Incorrect protein folding can lead to many human diseases. Alzheimer's disease is an example of a neurodegenerative condition caused by protein misfolding. This disease is characterized by dense plaques in the brain caused by misfolding of the secondary β-sheets of the fibrillar β-amyloid proteins present in brain matter. Huntington's disease and Parkinson's disease are other examples of neurodegenerative diseases associated with protein misfolding. Cystic fibrosis (CF) is a fatal disease caused by misfolding of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. In most cases of CF, the phenylalanine at position 508 of the CFTR is deleted, causing misfolding of the regulator protein. Several allergies have also been shown to be caused by incorrect protein folding. References
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Last Updated: Feb 26, 2019  Written by Susha CheriyedathSusha has a Bachelor of Science (B.Sc.) degree in Chemistry and Master of Science (M.Sc) degree in Biochemistry from the University of Calicut, India. She always had a keen interest in medical and health science. As part of her masters degree, she specialized in Biochemistry, with an emphasis on Microbiology, Physiology, Biotechnology, and Nutrition. In her spare time, she loves to cook up a storm in the kitchen with her super-messy baking experiments. CitationsPlease use one of the following formats to cite this article in your essay, paper or report:
Suggested ReadingWhich amino acids appear in protein bends?This is an important feature of protein folding, which gives a more compact shape. The β-turn is stabilised by a hydrogen bond between the first and third peptides. The amino acid proline is frequently found at bends in a protein backbone.
What is a folded chain of amino acids called?A protein molecule is made from a long chain of these amino acids, each linked to its neighbor through a covalent peptide bond (Figure 3-1). Proteins are therefore also known as polypeptides.
Where are amino acids in folded proteins?In proteins with globular folds, hydrophobic amino acids tend to be interspersed along the primary sequence, rather than randomly distributed or clustered together.
Which proteins are involved in protein folding?Proteins that facilitate the folding of other proteins are called molecular chaperones. The term “chaperone” was first used by Ron Laskey and his colleagues to describe a protein (nucleoplasmin) that is required for the assembly of nucleosomes from histones and DNA.
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Which of the following amino acids is found often in bends of folded protein chains?
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