Nucleotide-Free sB-Raf is Preferentially Bound by Hsp90 and Cdc37 In Vitro

Structure, Function, and Regulation of the Hsp90 Machinery

“…Kinases seem to require Hsp90 to maintain a specific active state (Grammatikakis et al 1999;Polier et al 2013;Boczek et al 2015). In the case of kinases, Hsp90 facilitates ATP binding by the kinase, which in turn stabilizes the kinase (Eckl et al 2016). Another category relies on Hsp90 for the assembly of protein complexes such as the kinetochore, the R2TP complex involved in snoRNP biogenesis, and also the purinosome required for purine biosynthesis (Kitagawa et al 1999;Zhao et al 2008;Pedley et al 2018).…”

“…How the open kinase conformation benefits activation is not entirely clear. One may speculate that the open conformation bound to Hsp90 represents an intermediate state that is required for ATP binding (Eckl et al 2016;Verba et al 2016). The Hsp90-dependent stabilization of this state could in turn be defined by the overall kinase stability and cooperativity of folding (Taipale et al 2012;Boczek et al 2015).…”

HSP-90/kinase complexes are stabilized by the large PPIase FKB-6

“…Nematode HSP-90 and CDC-37 form protein complexes with the stabilized kinase domain of sB-Raf and the complex has been found to be sensitive to the presence of ATP in previous studies 9 . To further understand the influence of nucleotides on the association of this important HSP-90•client complex, ATTO488-labeled sB-Raf (*sB-Raf) was generated and used to investigate the complex formation.…”

“…Based on our previous results 9 , nucleotides and chaperones interact with the kinase in an antagonizing way. When sB-Raf is in complex with ATP or ATP homologs, it is unable to bind to CDC-37.…”

“…The cofactor p23 instead can decelerate the ATPase cycle of Hsp90 8 , by stabilizing the dimerized conformation. Also the interaction between Hsp90 and Cdc37 is modulated by ATP, as the presence of ATP reduces the affinity between Hsp90 and Cdc37 9 .…”