Stress-70 proteins primary structure

Fig. I. Schematic drawing of the functional organization of stress-70 proteins within their primary structure. Numberscorrelate with the amino acid sequence of bovine HSC70.

It is conceivable that the participation of accessory proteins such as dnaj and grpE in some functions of dnaK will have parallels in the functions of other stress-70 proteins. Several dnaJ homologues have been documented in yeast, although as a group they do not show the stringent level of sequence conservation found in the stress-70 proteins. In particular, the primary structure of dnaj appears to be modular, and can be described as (1) an N-terminal region of 80-100 amino acid residues,... 

It is estimated that about 30% of the newly synthesized proteins are misfolded [27]. Protein misfoldings also occur due to partial unfolding during thermal or oxidative stress and also because of alterations in primary structure caused by mutation [28,29]. 

As the importance of ion-pairs toward protein thermostability has been stressed in many cases, addition or removal of an ion-pair should have significant effects. A clear example is provided by mutagenesis studies of glutamate dehydrogenase from T kodakaraensis KOD1 (Tk-GDH)[361. The GDH from Pyrococcus Juriosus (Pf-GDH) and Tk-GDH are 83% identical in terms of primary structure. However, while Pf GDH displays a half-life of 12 h at 100 C, that of Tk-GDH is 4 h. The three-... 

Conclusion. We have provided experimental evidence that the chaperonins meet the first criterion expected by their definition. They are molecules that, by their transient association with nascent, stress-destabilized or translocated proteins, prevent improper" aggregation. Chaperonins are not able to rescue aggregates once they are formed, nor do they appear to carry specific steric information, capable of directing a protein to assume a structure different from the one dictated by polypeptide primary sequence. 

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