Two-Step Activation Mechanism of the ClpB Disaggregase for Sequential Substrate Threading by the Main ATPase Motor

Two-Step Activation Mechanism of the ClpB Disaggregase for Sequential Substrate Threading by the Main ATPase Motor

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Summary: AAA+ proteins Nose Bands form asymmetric hexameric rings that hydrolyze ATP and thread substrate proteins through a central channel via mobile substrate-binding pore loops.Understanding how ATPase and threading activities are regulated and intertwined is key to understanding the AAA+ protein mechanism.We studied the disaggregase ClpB, which contains tandem ATPase domains (AAA1, AAA2) and shifts between low and high ATPase and threading activities.Coiled-coil M-domains repress ClpB activity by encircling the AAA1 ring.Here, we determine the mechanism of ClpB activation by comparing ATPase mechanisms and cryo-EM structures of ClpB wild-type and a constitutively active ClpB M-domain mutant.

We show that ClpB activation reduces ATPase cooperativity and induces a sequential mode of ATP hydrolysis in the AAA2 ring, the main ATPase motor.AAA1 and AAA2 rings do not work synchronously but in alternating cycles.This ensures high Bike Units - Road Aluminum grip, enabling substrate threading via a processive, rope-climbing mechanism.: ClpB is a ring-shaped protein threading machine involved in protein disaggregation, regulated by an encircling ring of coiled-coil M-domains repressing the ATPase domains.Deville et al.

determined a set of structures showing how ClpB activation by M-domain release triggers a sequential ATPase activity that translocates the polypeptide substrate.Keywords: protein disaggregation, protein unfolding, AAA+, Hsp100, chaperone, cryo-EM.