Tyrosine hydroxylase (TH) is a highly regulated enzyme that catalyses the rate-limiting step in the biosynthesis of dopamine (DA) and other catecholamines. Mutations and dysfunction in this enzyme lead to DA deficiency and parkinsonisms of different severity. An understanding of TH deficiency at the level of structure and stability has been lacking to date, as only structures of truncated TH forms have been available. Here, we used cryoEM to determine the first high-resolution structure of full-length human tetrameric TH in the absence (3.4 Å) and presence (3.8 Å) of the end-product and feedback inhibitor DA bound to the active site. We show that upon DA binding, an α-helix (residues 39-59) included within the flexible N-terminal tail of the regulatory domain, is internalized in the active site. The observed structural changes reveal the molecular basis of the inhibitory and stabilizing DA effect, reversible by TH S40-phosphorylation, which are crucial regulatory mechanisms for catecholamine and TH homeostasis.
The mechanistic target of rapamycin (mTOR) kinase forms two multi‐protein signaling complexes, mTORC1 and mTORC2, which are master regulators of cell growth, metabolism, survival and autophagy. Two of the subunits of these complexes are mLST8 and Raptor, β‐propeller proteins that stabilize the mTOR kinase and recruit substrates, respectively. Here we report that the eukaryotic chaperonin CCT plays a key role in mTORC assembly and signaling by folding both mLST8 and Raptor. A high resolution (4.0 Å) cryo‐EM structure of the human mLST8‐CCT intermediate isolated directly from cells shows mLST8 in a near‐native state bound to CCT deep within the folding chamber between the two CCT rings, and interacting mainly with the disordered N‐ and C‐termini of specific CCT subunits of both rings. These findings describe a unique function of CCT in mTORC assembly and a distinct binding site in CCT for mLST8, far from those found for similar β‐propeller proteins. Support or Funding Information This research was supported by the grant BFU2016‐75984 (AEI/FEDER, EU) and the Madrid Regional Government (grant S2013/MIT2807) to JMV as well as the US National Institutes of Health grant EY012287 to BMW and fellowships from the Brigham Young University Simmons Center for Cancer Research to WGL, NCT, TA and MD.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.