Abstract
Hsp104 disaggregase provides thermotolerance in yeast by recovering proteins from aggregates in cooperation with the Hsp70 chaperone. Protein disaggregation involves polypeptide extraction from aggregates and its translocation through the central channel of the Hsp104 hexamer. This process relies on adenosine triphosphate (ATP) hydrolysis. Considering that Hsp104 is characterized by low affinity towards ATP and is strongly inhibited by adenosine diphosphate (ADP), we asked how Hsp104 functions at the physiological levels of adenine nucleotides. We demonstrate that physiological levels of ADP highly limit Hsp104 activity. This inhibition, however, is moderated by the Hsp70 chaperone, which allows efficient disaggregation by supporting Hsp104 binding to aggregates but not to non-aggregated, disordered protein substrates. Our results point to an additional level of Hsp104 regulation by Hsp70, which restricts the potentially toxic protein unfolding activity of Hsp104 to the disaggregation process, providing the yeast protein-recovery system with substrate specificity and efficiency in ATP consumption.
Highlights
Molecular chaperones maintain protein homeostasis by supporting protein folding and preventing aggregation
Hsp104 consists of four domains: the N-terminal domain, two Nucleotide Binding Domains (NBD1 and NBD2) and a coiled coil region protruding from the NBD1, called the M-domain (Lee et al, 2003)
We show that the process of polypeptide threading by Hsp104 facilitates binding of adenosine triphosphate (ATP), strongly stimulating the ATPase activity of the disaggregase in the presence of adenosine diphosphate (ADP)
Summary
Molecular chaperones maintain protein homeostasis by supporting protein folding and preventing aggregation. During severe stress the capacity of this protective system becomes exhausted due to appearance of excess amounts of misfolded proteins and their aggregation. Hsp104 consists of four domains: the N-terminal domain, two Nucleotide Binding Domains (NBD1 and NBD2) and a coiled coil region protruding from the NBD1, called the M-domain (Lee et al, 2003). Hsp104 functions as a hexamer in which the Nucleotide Binding Domains form a double ring (Carroni et al, 2014; Lee et al, 2010; Parsell et al, 1994). During disaggregation a polypeptide is disentangled from the aggregate, translocated through the central channel, and enabled to fold into the native structure (Lum et al, 2004; Tessarz et al, 2008; Weibezahn et al, 2004)
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