Heat shock protein chaperone interaction

In addition to the intrinsic subunits, proteins that interact with the proteasome complex regulate its activity/ Often the cofactors are components of the ubiquitin pathway. Proteins such as chaperones and heat-shock proteins also assist in proteasome-mediated degradation of proteins. 

Pratt WB, Toft DO. (1997) Steroid receptor interactions with heat shock protein and immu-nophilin chaperones. Endocr Rev. 18, 306-360. 

Ballinger, C. A., P. Connell, Y. Wu, Z. Hu, L. J. Thompson, L. Y. Yin, and C. Patterson. Identification of CHIP, a novel tetratricopeptide repeat-containing protein that interacts with heat shock proteins and negatively regulates chaperone functions. Mol Cell Biol. 19 4535-45.1999. 

With the help of co-immimoprecipitation it could be shown that the receptors of steroid hormones interact with at least three chaperones, Hsp90, Hsp70 and Hsp56 (fig. 4.10). The term Hsp (Heat shock protein) is derived from the observation that these proteins were produced at higher levels following heat treatment. Furthermore, one finds a 23 kDa acidic protein in the apo-receptor complex whose fimction is not yet clear. 

Marcu, M.G. et al. 2000. The heat shock protein 90 antagonist novobiocin interacts with a previously unrecognized ATP-binding domain in the carboxyl terminus of the chaperone. J. Biol. Chem. 275, 37181-37186. 

Ubiquitin, found in several cellular compartments (e.g., cytoplasm and the nucleus), belongs to a class of proteins referred to as stress proteins. Stress proteins, also called heat shock proteins (hsp), are so named because their syntheses are accelerated (and in some cases initiated) when cells encounter stress. (The name heat shock protein is misleading, because a variety of stressful conditions besides elevated temperature induce their synthesis.) Other stress proteins act as molecular chaperones, that is, they promote protein folding (p. 692). Heat shock proteins and molecular chaperones also play significant roles in protein transport and intermolecular interactions. 

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