Abstract
Studies on Hsp90 have mainly focused on its involvement in the activation of several families of protein kinases and of steroid hormone receptors. Little is known regarding the role of Hsp90 in the folding of nascent proteins. We previously reported that Hsp90 plays an active role in the posttranslational assembly of the C-terminal globular head of the reovirus attachment protein final sigma1. We show here that Hsp90 becomes phosphorylated in this process. However, only the unphosphorylated form of Hsp90 is complexed with final sigma1, suggesting that Hsp90 phosphorylation is coupled to the release of the chaperone from the target protein. Geldanamycin, which blocks final sigma1 maturation by preventing the release of Hsp90 from final sigma1, also inhibits Hsp90 phosphorylation. Taken together, these results demonstrate that Hsp90 phosphorylation is linked to its chaperoning function.
Highlights
Studies on Hsp90 have mainly focused on its involvement in the activation of several families of protein kinases and of steroid hormone receptors
At the time point chosen for immunoprecipitation, prior studies have shown that the majority of the 1 protein has trimerized within the N-terminal coiled-coil domain and a subpopulation has progressed to the mature form that has folded within the C-terminal globular domain
We investigate the possibility that Hsp90 phosphorylation is linked to its chaperoning function, in the folding and assembly of nascent polypeptides
Summary
Cellular chaperones are a group of proteins whose major roles appear to be the prevention of target protein aggregation and the promotion of their correct folding and assembly [1,2,3] Chaperones such as Hsp and Hsp likely interact with a wide variety of polypeptides, and their involvement in the folding processes is believed to be of a general and universal nature. Subsequent ATP-dependent release of chaperones presumably provides the opportunity for the loose coiled-coil to quickly snap together (tightening the coiled-coil), whereas the remaining portions of the three C termini are available for continued interaction with chaperones This structure, with a stably assembled N terminus and an unassembled C terminus, is called “stable hydra form,” and it migrates as a retarded trimer in SDS-PAGE under nondissociating conditions. These observations have led us to propose that Hsp phosphorylation is linked to its chaperoning function
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
