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Mechanism for autoinhibition and activation of the MORC3 ATPase.

ABSTRACT: Microrchidia 3 (MORC3) is a human protein linked to autoimmune disorders, Down syndrome, and cancer. It is a member of a newly identified family of human ATPases with an uncharacterized mechanism of action. Here, we elucidate the molecular basis for inhibition and activation of MORC3. The crystal structure of the MORC3 region encompassing the ATPase and CW domains in complex with a nonhydrolyzable ATP analog demonstrates that the two domains are directly coupled. The extensive ATPase:CW interface stabilizes the protein fold but inhibits the catalytic activity of MORC3. Enzymatic, NMR, mutational, and biochemical analyses show that in the autoinhibited, off state, the CW domain sterically impedes binding of the ATPase domain to DNA, which in turn is required for the catalytic activity. MORC3 autoinhibition is released by disrupting the intramolecular ATPase:CW coupling through the competitive interaction of CW with histone H3 tail or by mutating the interfacial residues. Binding of CW to H3 leads to a marked rearrangement in the ATPase-CW cassette, which frees the DNA-binding site in active MORC3 (on state). We show that ATP-induced dimerization of the ATPase domain is strictly required for the catalytic activity and that the dimeric form of ATPase-CW might cooperatively bind to dsDNA. Together, our findings uncovered a mechanism underlying the fine-tuned regulation of the catalytic domain of MORC3 by the epigenetic reader, CW.

SUBMITTER: Zhang Y

PROVIDER: S-EPMC6442546 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Mechanism for autoinhibition and activation of the MORC3 ATPase.

Zhang Yi Y Klein Brianna J BJ Cox Khan L KL Bertulat Bianca B Tencer Adam H AH Holden Michael R MR Wright Gregory M GM Black Joshua J Cardoso M Cristina MC Poirier Michael G MG Kutateladze Tatiana G TG

Proceedings of the National Academy of Sciences of the United States of America 20190308 13

Microrchidia 3 (MORC3) is a human protein linked to autoimmune disorders, Down syndrome, and cancer. It is a member of a newly identified family of human ATPases with an uncharacterized mechanism of action. Here, we elucidate the molecular basis for inhibition and activation of MORC3. The crystal structure of the MORC3 region encompassing the ATPase and CW domains in complex with a nonhydrolyzable ATP analog demonstrates that the two domains are directly coupled. The extensive ATPase:CW interfac ...[more]

PMID: 30850548

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Project description:The S. cerevisiae plasma membrane H+-ATPase, Pma1, is a P3A-type ATPase and the primary protein component of the membrane compartment of Pma1 (MCP). Like other plasma membrane H+-ATPases, Pma1 assembles and functions as a hexamer, a property unique to this subfamily among the larger family of P-type ATPases. It has been unclear how Pma1 organizes the yeast membrane into MCP microdomains, or why it is that Pma1 needs to assemble into a hexamer to establish the membrane electrochemical proton gradient. Here we report a high-resolution cryo-EM study of native Pma1 hexamers embedded in endogenous lipids. Remarkably, we found that the Pma1 hexamer encircles a liquid-crystalline membrane domain composed of 57 ordered lipid molecules. The Pma1-encircled lipid patch structure likely serves as the building block of the MCP. At pH 7.4, the carboxyl-terminal regulatory α-helix binds to the phosphorylation domains of two neighboring Pma1 subunits, locking the hexamer in the autoinhibited state. The regulatory helix becomes disordered at lower pH, leading to activation of the Pma1 hexamer. The activation process is accompanied by a 6.7 Å downward shift and a 40° rotation of transmembrane helices 1 and 2 that line the proton translocation path. The conformational changes have enabled us to propose a detailed mechanism for ATP-hydrolysis-driven proton pumping across the plasma membrane. Our structures will facilitate the development of antifungal drugs that target this essential protein. The plasma membrane H+ -ATPase is responsible for maintenance of the plasma membrane potential, which provides energy for the transport of nutrients, and the plasma membrane H+ -ATPase in S. cerevisiae (Pma1) is a P3A-type ATPase that assembles and functions as a hexamer. Here, the authors present the cryo-EM structures of autoinhibited and activated native Pma1 hexamers purified with endogenous lipids and they propose a mechanism for proton pumping across the membrane by this family of H+ -ATPases.

Dataset Information

Mechanism for autoinhibition and activation of the MORC3 ATPase.

Publications

Mechanism for autoinhibition and activation of the MORC3 ATPase.

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