Functional analysis of conserved cis- and trans-elements in the Hsp104 protein disaggregating machine.
Hsp104 is a double ring-forming AAA+ ATPase, which harnesses the energy of ATP binding and hydrolysis to rescue proteins from a previously aggregated state. Like other AAA+ machines, Hsp104 features conserved cis- and trans-acting elements, which are hallmarks of AAA+ members and are essential to Hsp104 function. Despite these similarities, it was recently proposed that Hsp104 is an atypical AAA+ ATPase, which markedly differs in 3D structure from other AAA+ machines. Consequently, it was proposed that arginines found in the non-conserved M-domain, but not the predicted Arg-fingers, serve the role of the critical trans-acting element in Hsp104. While the structural discrepancy has been resolved, the role of the Arg-finger residues in Hsp104 remains controversial. Here, we exploited the ability of Hsp104 variants featuring mutations in one ring to retain ATPase and chaperone activities, to elucidate the functional role of the predicted Arg-finger residues. We found that the evolutionarily conserved Arg-fingers are absolutely essential for ATP hydrolysis but are dispensable for hexamer assembly in Hsp104. On the other hand, M-domain arginines are not strictly required for ATP hydrolysis and affect the ATPase and chaperone activities in a complex manner. Our results confirm that Hsp104 is not an atypical AAA+ ATPase, and uses conserved structural elements common to diverse AAA+ machines to drive the mechanical unfolding of aggregated proteins.
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
Amadeo B
AB
Biter
Jungsoon
J
Lee
Nuri
N
Sung
Francis T F
FT
Tsai
Sukyeong
S
Lee
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
D006360:Heat-Shock Proteins; D000251:Adenosine Triphosphatases