Stress GroEL

Many of the chaperones double as heat shock-proteins (Hsp). When a cell is put under stress that can cause proteins to denature, such as too high a temperature, it produces heat-shock proteins. Their names are abbreviated to Hsp plus their subunit molecular mass in kDa. Hsp70, for example, is a ubiquitous heat-shock protein in eukaryotes. It is known in E. coli as DnaK for historical reasons because it was first discovered from a supposed role in DNA replication. Hsp70 is also important in protein trafficking and the conveying of proteins across membranes, because the denatured state is important in these processes. In protein biosynthesis, the unfolded state of the nascent polypeptide chain is passed on to DnaK, which maintains it in an extended form. The chain, under the influence of ATP and co-chaperones such as DnaJ and GrpE, is handed over to GroEL. 

Salotra, P., D.K. Singh, K.P, Seal, N. Krishna, H. Jaffe, and R. Bhatnagar (1995). Expression of DnaK and GroEL homologs in Leuconostoc mesenteriodes in response to heat-shock, cold-shock or chemical stress. FEMS Microbiol. Lettr. 131 57-62. 

Susin, M.F., Baldini, R.L., Gueiros-Filho, F., Gomes, S.L. (2006). GroES/GroEL and DnaK/DnaJ have distinct roles in stress responses and during cell cycle progression in Caulobacter crescentus. J. Bacterial. 188 8044-53. 

Stress protein molecular chaperones have already been introduced (see Chapter 6). Such proteins have a rich and varied molecular recognition and binding behaviour. Important examples include GroEL and the procollagen/collagen molecular chaperone protein known as heat shock protein 47 (Hsp47). 

From this viewpoint, the heat-induced translocation of cytoplasmic -galactosi-dase across the inner membrane of Escherichia coli has been investigated [9-12]. The cell membrane [13,14] under stress condition has also been studied, where the possible roles of GroEL and other chaperones have also been discussed [12]. In order... 

Kovdcs E, Torok Z, Horvath I, Vigh L. Heat stress induces association of the GroEL-analog chaperonin with thylakoid membranes in cyanobacterium, Synechocystis PCC 6803. Plant Physiol.Biochem. 1994 32 285-293. 

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