G protein coupled receptors (GPCRs) exhibit a spectrum of functional behaviors in response to natural and synthetic ligands. Recent crystal structures provide insights into inactive states of several GPCRs. Efforts to obtain an agonist-bound active-state GPCR structure have proven difficult due to the inherent instability of this state in the absence of a G protein. We generated a camelid antibody fragment (nanobody) to the human β2 adrenergic receptor (β2AR) that exhibits G protein-like behavior, and obtained an agonist-bound, active-state crystal structure of the receptor-nanobody complex. Comparison with the inactive β2AR structure reveals subtle changes in the binding pocket; however, these small changes are associated with an 11Å outward movement of the cytoplasmic end of transmembrane segment 6, and rearrangements of transmembrane segments 5 and 7 that are remarkably similar to those observed in opsin, an active form of rhodopsin. This structure provides insights into the process of agonist binding and activation.
Idiopathic pulmonary fibrosis (IPF) is a progressive and ultimately fatal disease characterised by fibrosis of the lung parenchyma and loss of lung function. Although the pathogenic pathways involved in IPF have not been fully elucidated, IPF is believed to be caused by repetitive alveolar epithelial cell injury and dysregulated repair, in which there is uncontrolled proliferation of lung fibroblasts and differentiation of fibroblasts into myofibroblasts, which excessively deposit extracellular matrix (ECM) proteins in the interstitial space. A number of profibrotic mediators including platelet-derived growth factor (PDGF), fibroblast growth factor (FGF) and transforming growth factor-β are believed to play important roles in the pathogenesis of IPF. Nintedanib is a potent small molecule inhibitor of the receptor tyrosine kinases PDGF receptor, FGF receptor and vascular endothelial growth factor receptor. Data from in vitro studies have shown that nintedanib interferes with processes active in fibrosis such as fibroblast proliferation, migration and differentiation, and the secretion of ECM. In addition, nintedanib has shown consistent anti-fibrotic and anti-inflammatory activity in animal models of lung fibrosis. These data provide a strong rationale for the clinical efficacy of nintedanib in patients with IPF, which has recently been demonstrated in phase III clinical trials.
The outer membrane protein A of Escherichia coli (OmpA) is an intensely studied example in the field of membrane protein folding. We have determined the structure of the OmpA transmembrane domain consisting of residues 1-171, by X-ray diffraction analysis, to a resolution of 2.5 A. It consists of a regular, extended eight-stranded beta-barrel and appears to be constructed like an inverse micelle with large water-filled cavities, but does not form a pore. Surprisingly, the cavities seem to be highly conserved during evolution. The structure corroborates the concept that all outer membrane proteins consist of beta-barrels. The structure constitutes a beta-barrel membrane anchor that appears to be the outer membrane equivalent of the single-chain alpha-helix anchor of the inner membrane.
SummaryHuntingtin (Htt) is a large (348 kDa) protein, essential for embryonic development and involved in diverse cellular activities such as vesicular transport, endocytosis, autophagy and transcription regulation1,2. While an integrative understanding of Htt's biological functions is lacking, the large number of identified interactors suggests that Htt serves as a protein-protein interaction hub1,3,4. Furthermore, Huntington’s disease is caused by a mutation in the Htt gene, resulting in a pathogenic expansion of a polyglutamine (polyQ) repeat at the N-terminus of Htt5,6. However, only limited structural information on Htt is currently available. Here we employed cryo-electron microscopy (cryo-EM) to determine the structure of full-length human Htt in a complex with HAP40/F8A7 to 4 Å resolution. Htt is largely α-helical and consists of three major domains. The N- and C-terminal domains contain multiple HEAT repeats arranged in a solenoid fashion. These domains are connected by a smaller bridge domain containing different types of tandem repeats. HAP40 is also largely α-helical and has a tetratricopeptide repeat (TPR)-like organization. HAP40 binds in a cleft contacting the three Htt domains by hydrophobic and electrostatic interactions, thereby stabilizing Htt conformation. These data rationalize previous biochemical results and pave the way for an improved understanding of Htt’s diverse cellular functions.
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.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.