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Heat shock proteins are also believed to play a role in the presentation of pieces of proteins (or peptides) on the cell surface to help the immune system recognize diseased cells. [22] The major HSPs involved in the HSR include HSP70, HSP90, and HSP60. [5] Chaperones include the HSP70s and HSP90s while HSP60s are considered to be chaperonins. [17]
In biochemistry, denaturation is a process in which proteins or nucleic acids lose folded structure present in their native state due to various factors, including application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), agitation and radiation, or heat. [3]
The heat shock response involves a class of stress proteins called heat shock proteins. [4] [5] These can help defend a cell against damage by acting as 'chaperons' in protein folding, ensuring that proteins assume their necessary shape and do not become denatured. [6]
Heat shock proteins (HSPs) are a family of proteins produced by cells in response to exposure to stressful conditions. They were first described in relation to heat shock , [ 1 ] but are now known to also be expressed during other stresses including exposure to cold, [ 2 ] UV light [ 3 ] and during wound healing or tissue remodeling. [ 4 ]
Its molecular weight is about 90 kDa, and it is necessary for viability in eukaryotes (possibly for prokaryotes as well). Heat shock protein 90 (Hsp90) is a molecular chaperone essential for activating many signaling proteins in the eukaryotic cell. Each Hsp90 has an ATP-binding domain, a middle domain, and a dimerization domain.
Hsp70 proteins can act to protect cells from thermal or oxidative stress. These stresses normally act to damage proteins, causing partial unfolding and possible aggregation. By temporarily binding to hydrophobic residues exposed by stress, Hsp70 prevents these partially denatured proteins from aggregating, and inhibits them from refolding.
At high temperatures, these interactions cannot form, and a functional protein is denatured. [25] However, it relies on two factors; the type of protein used and the amount of heat applied. The amount of heat applied determines whether this change in protein is permanent or if it can be transformed back to its original form. [26]
Heat inactivation reduces extension transverse to cellulose microfibril orientation but does not reduce parallel extension. This indicates that heat inactivation has a directional effect on cell wall extension. In the transverse direction, extension depends on proteins, as denatured proteins cause reduced extension.