How the cell copes with stress and the function of heat shock proteins

摘要: ABSTRACT: Virtually all cells, including the prokaryotic microorganisms and highly differentiated eukaryotic cells in human tissues, contain a small set of normally silent genes that are rapidly activated by heat shock raises temperature only 5 to 10% above normal physiologic range for organism. Concomitantly, many active turned off. Other kinds stress, such as exposure alcohol or other organic agents, heavy metals, oxidants, agents capable perturbing protein structure, produce similar response, these activate same genes. The proteins encoded stress-activated called (hsp). They strongly conserved structure among widely divergent biologic species, function “molecular chaperones” forming transient complexes with partially folded misfolded polypeptides so prevent their irreversible denaturation. Most hsp members gene/protein families, isoforms frequently found under conditions compartments cell where they act also chaperones, binding variety facilitate folding, oligomerization, transport, metabolic activity, degradation. Few polypeptide “targets” complex stress-induced forms have been identified, but number cellular components shown be particularly stress sensitive. include macromolecular involved maintenance chromosome replication transcription, mRNA splicing, ribosome assembly. Mitochondria intermediate filament network sensitive, whereas synthetic machinery vesicles secretory pathway relative stable stress. factors regulating eukaryote species promoters consisting arrays short, inverted sequences DNA, element, factors, which large occupy soon after senses shift. sensor(s) signal initiate thereby activating gene not postulated play key role this event. response is transient, down-regulate system. Cells mildly prestressed significant levels become tolerant would kill cell. In way, organisms survive environmental might otherwise prove fatal.