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Principles of Chemistry
Published in Arthur T. Johnson, Biology for Engineers, 2019
Proteins are originally synthesized inside ribosomes in the cytoplasm or inside the endoplasmic reticulum (ER). The latter synthesize proteins intended to be embedded in the cell membrane (Conn and Jamovick, 2005). When released from the ribosomes, the protein backbone first folds in groups of four or more amino acids to limit interference from bulky or charge-bearing portions of the molecule. Chaperone molecules assist the proteins to fold into their correct three-dimensional shapes. This is especially difficult among the molecules crowded inside the cell. Chaperone molecules work by encasing an unfolded protein in an isolation compartment. Safely inside, the proteins fold correctly by themselves. Without the isolation, the proteins clump together and kill the cell (Goforth, 2012).
General Introductory Topics
Published in Vadim Backman, Adam Wax, Hao F. Zhang, A Laboratory Manual in Biophotonics, 2018
Vadim Backman, Adam Wax, Hao F. Zhang
Following translation on a ribosome, a protein must undergo posttranslational modifications and folding. Protein folding is an extremely complex process, as the three-dimensional structure of proteins is of crucial importance to their function. Chaperones are special protein complexes that help proteins fold correctly. High density of intracellular environment, called molecular crowding, helps increase the rate of folding. Without crowding, if left to their own devices, the time required for proteins to fold would be dramatically increased. Indeed, approximately 30% of the space inside a cell is physically occupied by macromolecules. Due to steric interactions and volume exclusion, most of the remaining space is excluded for macromolecular interactions. As a result, as little as 1% of cell volume remains for macromolecular processes such as mRNA diffusion and protein folding to take place. An increase or decrease in the available volume is expected to significantly change many cellular processes.
Introduction and Background
Published in Jay L. Nadeau, Introduction to Experimental Biophysics, 2017
How proteins fold is an extremely complex subject, and many sophisticated resources exist on the topic, of which we reference a few at the end of this chapter. It was originally believed that all of the information for the tertiary structure was contained within the primary structure, but this turned out only to be the case for relatively small, soluble proteins. More complex proteins require the assistance of enzymes, called chaperones, to fold properly and reach their final destination without aggregating. Chaperones assist proteins in finding their native conformation, assist refolding of misfolded proteins, and bind to the hydrophobic surfaces of proteins in order to prevent aggregation. Other types of posttranslational processing of the polypeptide chain may also be necessary to produce an active protein. These include proteolytic cleavage (enzymes called proteases trim the ends of the polypeptide chain, or cut it into smaller pieces) and chemical modifications in which new chemical groups are added to specific amino acid residues. Some chemical modifications, such as phosphorylation (addition of a phosphate group), are simple and are performed by all organisms. More complex modifications such as glycosylation (addition of a large carbohydrate side chain) are only performed in eukaryotic cells.
Using chemical chaperones to increase recombinant human erythropoietin secretion in CHO cell line
Published in Preparative Biochemistry and Biotechnology, 2019
Mehri Mortazavi, Mohammad Ali Shokrgozar, Soroush Sardari, Kayhan Azadmanesh, Reza Mahdian, Hooman Kaghazian, Seyed Nezamedin Hosseini, Mohammad Hossein Hedayati
Chemical chaperones are small molecules that assist molecular chaperones to fold a protein in endoplasmic reticulum also integrate into the protein structure to protect its folding in the secretory pathway. Molecular chaperones and chemical chaperones collaborate with each other to reduce misfolded protein response and enhance protein secretion.[5,15] Such collaboration happens as a result of the increased activity of molecular chaperones after treatment of the cells by chemical chaperone. Also chemical chaperones cooperate with molecular chaperones by adjust their activity.[16] Chemical chaperones are from different groups of components, including polyols such as glycerol, methylamines such as trimethylamine N-oxide (TMAO), sugar, and amino acid derivatives. It is worth mentioning that media optimization is currently the most important plan in recombinant protein production using CHO cell line. The existing challenges in bioprocessing tasks such as low yield and aggregation can be studied and resolved to improve protein production using chemical chaperones through handling molecular chaperones.[3]
Improving the soluble expression of aequorin in Escherichia coli using the chaperone-based approach by co-expression with artemin
Published in Preparative Biochemistry and Biotechnology, 2018
Elaheh Khosrowabadi, Zeinab Takalloo, Reza H. Sajedi, Khosro Khajeh
Different strategies have been presented to reduce protein aggregation. The most popular approaches involve using chaperones and stabilizing agents, optimizing growth, and using fusion proteins.[1] Since formation of inclusion bodies might be a conformational or folding issue,[2] co-expression of the susceptible proteins with chaperones in a single host has become a widespread approach.[6] Chaperones have been applied successfully to facilitate the folding of many recombinant proteins and reduce aggregation of the proteins and prevent the accumulation of the aggregates.[7–11] It is assumed that chaperones inhibit the inclusion body formation of proteins due to their ability to bind and maintain partially folded intermediates and prevent their aggregation.[12]
Expression of genes related to antioxidant activity in Nile tilapia kept under salinity stress and fed diets containing different levels of vitamin C
Published in Journal of Toxicology and Environmental Health, Part A, 2018
Caio Alexandre Santos Caxico Vieira, Jodnes Sobreira Vieira, Marisa Silva Bastos, Vittor Zancanela, Leandro Teixeira Barbosa, Eliane Gasparino, Ana Paula Del Vesco
In contrast to antioxidant enzymes, after only 24 h, tilapia maintained in 21‰ salinity presented higher HSP70 gene expression. Heat shock proteins (HSPs) act as molecular chaperones under normal conditions, playing a crucial role in protein folding and dealing with damaged proteins. However, these proteins are largely produced as a consequence of stress situations reacting to a broad range of stressors including temperature, UV radiation, hypoxia, inflammation, infections, chemical pollutants, and salinity. In these situations, HSPs play a role in repair and protection as well as in the degradation of poorly enveloped proteins whose damage is not reversible (Pirkkala and Sistonen 2006; Varasteh et al. 2015). Thus, exposure to any of these factors induces HSP synthesis and increases cell protection (Di Giulio and Hinton 2008). In addition, Deane et al. (2002) noted that salinity stress by itself may determine whether the heat shock response of an organism is augmented or attenuated during exposure to other stressors. Indeed, under salinity stress, HSPs may be associated with other factors since a positive correlation between HSP70 and Na+,K+/ATPase gene expression was found in the gill of black-chinned tilapia (Sarotherodon melanotheron) exposed to salinity conditions (Tine et al. 2010). Tine et al. (2010) also observed that the highest HSP70 and Na+,K+/ATPase mRNA levels were present in the poorest CF situations at 21‰ salinity without vitamin C supplementation. This treatment also had the highest expression of HSP70 gene levels after 24 h.