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Orders Norzivirales and Timlovirales
Published in Paul Pumpens, Peter Pushko, Philippe Le Mercier, Virus-Like Particles, 2022
Paul Pumpens, Peter Pushko, Philippe Le Mercier
Furthermore, the Francis team encapsulated enzymes inside the MS2 capsids, using a new osmolyte-based method (Glasgow et al. 2012). Attaching DNA oligomers to a molecule of interest and incubating it with the MS2 coat protein dimers in vitro yielded reassembled capsids that packaged the tagged molecules. The addition of a protein-stabilizing osmolyte, trimethylamine-N-oxide, significantly increased the yields of reassembly. Second, the expressed proteins with genetically encoded negatively charged peptide tags could also induce capsid reassembly, resulting in high yields of reassembled capsids containing the protein. This second method was used to encapsulate alkaline phosphatase tagged with a 16-aa peptide. The purified encapsulated enzyme was found to have the same Km value and a slightly lower kcat value than the free enzyme, indicating that this method of encapsulation had a minimal effect on the enzyme kinetics. This method therefore provided a practical and potentially scalable way of studying the complex effects of encapsulating enzymes in protein-based compartments (Glasgow et al. 2012).
Chimeric VLPs
Published in Paul Pumpens, Single-Stranded RNA Phages, 2020
Another method of protein encapsidation was demonstrated by Francis’ team with the MS2 capsids (Glasgow et al. 2012). Thus, the two improved methods for the encapsulation of heterologous molecules inside the MS2 capsids were elaborated. First, attaching DNA oligomers to a molecule of interest and incubating it with MS2 coat protein dimers yielded reassembled capsids that packaged the tagged molecules. The addition of a protein-stabilizing osmolyte, trimethylamine-N-oxide, significantly increased the yields of reassembly. Second, it was found that the expressed proteins with genetically-encoded negatively-charged peptide tags could also induce capsid reassembly, resulting in high yields of reassembled capsids containing the protein. This second method was used to encapsulate alkaline phosphatase tagged with a 16-amino acid peptide. The purified encapsulated enzyme was found to have the same Km value and a slightly lower kcat value than the free enzyme, indicating that this method of encapsidation had a minimal effect on enzyme kinetics (Glasgow et al. 2012).
Creatine supplementation in sport, exercise and health
Published in Jay R Hoffman, Dietary Supplementation in Sport and Exercise, 2019
Eric S Rawson, Eimear Dolan, Bryan Saunders, Meghan E Williams, Bruno Gualano
Other adverse effects have been theorized and should be discussed before decisions regarding the suitability of this supplement are made. Many of these theoretical concerns relate to the osmolyte activity of creatine. As described previously, creatine is an osmotically-active substance, which increases intracellular fluid content. Anecdotal reports of muscle cramping or injuries resulting from theoretical fluid or electrolyte imbalances have not been supported by controlled trials (47, 66, 107). Cases of rhabdomyolysis have been reported, but these cases are confounded by other well-known causes such as drug use, dehydration, extreme exercise and traumatic injury (107). The effects of creatine supplementation on muscle damage and recovery in response to extreme exercise have been well studied, with no study showing increased muscle damage or dysfunction in creatine loaded subjects (107). In fact, several studies show enhanced recovery or decreased damage and inflammation in creatine supplemented individuals undergoing stressful exercise.
Protein misfolding, ER stress and chaperones: an approach to develop chaperone-based therapeutics for Alzheimer’s disease
Published in International Journal of Neuroscience, 2023
Rimaljot Singh, Navpreet Kaur, Neelima Dhingra, Tanzeer Kaur
To begin, focusing on the mechanisms of action of various chemical chaperones, osmolytes are known to exert their effect in two ways: directly or indirectly. The intracellular milieu is enriched with organic osmolytes under denaturing stress conditions and these osmolytes are known to enhance the protein’s stability without interfering with its activity. Some osmolytes have been shown to induce heat shock proteins as well as intracellular osmolytes, which are believed to improve protein folding performance under different cellular stresses, at low concentrations. Problems involving mutant protein folding cannot be improved by such an indirect mechanism; hence, for the direct mechanism to function, osmolytes must penetrate the cell membrane through osmolyte transporters present on the cell membrane. TMAO and glycerol, on the other hand, work by interacting thermodynamically with the proteins and stabilizing the native protein’s equilibrium state in vitro. These thermodynamic changes can occur at various stages in the in vitro state, such as protein stabilization in the unfolded state. A mutation allows the intermediate structures to accumulate in the ER, resulting in inefficient folding. Once folded, the mutant proteins trigger their most stable form; hence, the mutation is unlikely to destabilize the native structure [136].
Osmolyte taurine induction in UVA exposed human retinal pigment epithelial cells
Published in Cutaneous and Ocular Toxicology, 2018
Compatible osmolytes are present in the retina to maintain retinal intercellular homeostasis. This study found that RPE cells expressed osmolyte transporters, including BGT-1, SMIT, and TAUT, which led to the uptake of the respective osmolytes. Increased osmolyte accumulation under hypertonicity and UVA exposure is the result of an increased uptake mechanism caused by the expression of specific osmolyte transporters and the uptake mechanisms far exceed the efflux components. Remarkably, UVA increased the synthesis of transporter proteins rather than the transient activation of originally present transporters. Compatible osmolytes refer to betaine, myoinositol, and taurine in RPE cells. We previously showed that compatible osmolytes are related to osmotic homeostasis, volumetric homeostasis, and cellular protection because osmolytes are considered small molecular chaperones that resist oxidative stress and protect native macromolecular protein structures17. Moreover, osmolytes are considered to play a role in development18,19. The lens exhibited a defective elongation process in the absence of osmotic-response element-binding protein (OREBP) and sufficient osmolytes20. In this regard, osmolytes may ensure normal development and protect cells against various types of damage.
Taurine reduces blue light-induced retinal neuronal cell apoptosis in vitro
Published in Cutaneous and Ocular Toxicology, 2018
Betaine, myoinositol, and taurine are uncharged osmolytes. Osmolytes play protective roles in many tissues and cells under various conditions. The corresponding transporters responsible for osmolyte transport include the betaine/GABA transporter (BGT-1), sodium/myoinositol cotransporter (SMIT), and taurine transporter (TAUT). The organic osmolyte betaine stabilizes corneal epithelial cell volume under hyperosmotic stress and limits hyperosmotic stress-induced human corneal epithelial cell apoptosis4. Medullary cells accumulate massive amounts of organic osmolytes to survive in extremely hypertonic, hostile conditions5. Betaine controls unique gene expression pathways, including some involved in epidermal keratinocyte differentiation, which may counteract UV-induced damage processes in the skin6. The organic osmolyte taurine is critically involved in photoprotection of the skin7. Osmolytes are also involved in regulation of immunological processes8. In addition, protein stabilization by osmolytes may ensure monoclonal antibody stability9. Osmolytes exhibit protective effects on the skin, kidney, and immune system.