stress response of Saccharomyces cerevisiae
... In fact, any thing that causes stress to a cell will cause the cell to activate the expression of its protective proteins called Heat shock or Heat stress proteins (1). Initially the discovery was made 30 years ago when cells were subjected to an increase in temperature in their immediate environment, and an increase in the heat stress proteins was observed. However further studies demonstrated that the same response from the cells was observed when they were subjected to a variety of assaults such as toxic metals, alcohol’s, and metabolic poisons, i. ... More recently, biologists have discovered that many of these proteins that participate in the heat stress response also are indirectly involved in essential metabolic processes, including the pathways in which cellular proteins are synthesised. Some of the stress proteins also appear to orchestrate the activities of molecules that regulate cell growth and differentiation. In a study conducted by Hightower, he suggested that the accumulation of denatured or abnormally folded proteins in a cell initiate a stress response, which may facilitate the identification and removal of denatured proteins from the traumatised cell. ... Thus most of the heat stress proteins are expressed constitutively in all cells under normal growth conditions, but through a stress response they exhibit a higher level of expression whenever the cell is faced with unfavourable conditions for protein folding and association, i. ... increasing temperature, agents which attack sulphydryl groups and a large number of toxic agents which result in a reduction in ATP levels Heat stress protein’s are named based upon their molecular weight and are grouped in to families, the most common family being HSP70. ... In Saccharomyces cerevisiae there are six Hsp70 homologies in the cytosol (SSA1-SSA4, SSB1 and SSB2)and in the mitochondria (SSC1p) and in the endoplasmic reticulum (Kar2). ... The first proteins recognised to be involved in Heat shock response were Hsp60, and as with Hsp70 these are found in all organisms. ... There are also some glycolytic enzymes, ubiquitin and a plasma membrane protein, which are strongly induced upon exposing cells to stress; the reasons for this are not fully understood. ... Moreover an increasing number of proteins that respond to stress are being discovered. This experiment involved inducing the heat stress response in yeast cells Saccharomyces cerevisiae by treating them to 37 °C with 10 minutes shaking (universal A), treating a second batch of cells at 43 °C for 10 minutes shaking (universal B), a third batch were treat with 1mg/ml of tunicamycin and incubated for 1/2 hour (universal c). ... The aim being to identify any expressed Hsp’s in the cells by analysing the proteins present in the Saccharomyces cerevisiae cells after treatment, by SDS-PAGE gel electrophoresis. ... The spectrum of Hsp synthesis in yeast resulting from a stress challenge is similar to that of other eukaryotes and prokaryotes. ... The results for B and C are of low protein concentration, which is as expected as these cells were subjected to much stress treatment. ... The sample with the least protein expression is sample C, and most of the bands are similar to protein bands in sample B, thus suggesting that the treatments to the cells in B and C have brought about a similar response. ... This includes some of the Heat Stress Proteins (Hsp) which are expressed in the cell under normal conditions, i. ... In a study by McAlister et al in 1979 the response of Hsp expression at 36°C was similar to the response in this experiment. ... thermal injury or other stress factors that may follow. ... Hsp83, Hsp30, and Hsp12 were expressed at both 37° c and 43° C suggesting that they play important roles in the stress response especially at elevated temperatures. ... Hsp104 is also thought to protect the nuclei as it is increased not only under stress but when cells are induced to sporulate. Under stress conditions, Hsp104 is thought to have a similar role to Hsp70 in that they prevent the formation of protein aggregates or promote the dissolution of protein aggregates and stabilise unfolded protein conformations. ... , that under ideal conditions for a yeast cell to deal with the stress, Hsp70 captures the endangered proteins as they unfold, stabilises them and passes them to Hsp100 for refolding.