Institute of Structural & Molecular Biology, Department of Structural & Molecular Biology, University College London, London, UK and Department of Biological Sciences, Birkbeck College, London, UK.
Published: October 2022
AI Article Synopsis
Article Abstract
Co-translational folding is crucial to ensure the production of biologically active proteins. The ribosome can alter the folding pathways of nascent polypeptide chains, yet a structural understanding remains largely inaccessible experimentally. We have developed site-specific labelling of nascent chains to detect and measure, using F nuclear magnetic resonance (NMR) spectroscopy, multiple states accessed by an immunoglobulin-like domain within a tandem repeat protein during biosynthesis. By examining ribosomes arrested at different stages during translation of this common structural motif, we observe highly broadened NMR resonances attributable to two previously unidentified intermediates, which are stably populated across a wide folding transition. Using molecular dynamics simulations and corroborated by cryo-electron microscopy, we obtain models of these partially folded states, enabling experimental verification of a ribosome-binding site that contributes to their high stabilities. We thus demonstrate a mechanism by which the ribosome could thermodynamically regulate folding and other co-translational processes.
Glutathione (GSH) is an abundant thiol-containing tripeptide that functions in redox homeostasis, protein folding, and iron metabolism. In Saccharomyces cerevisiae, GSH depletion leads to increased sensitivity to oxidants and other toxic compounds, disruption of Fe-S cluster biogenesis, and eventually cell death. GSH pools are supplied by intracellular biosynthesis and GSH import from the extracellular environment.
Aims: Osteogenesis imperfecta (OI) is a collagen I-related heritable family of skeletal diseases associated to extreme bone fragility and deformity. Its classical forms are caused by dominant mutations in COL1A1 and COL1A2, which encode for the protein α chains, and are characterized by impairment in collagen I structure, folding, and secretion. Mutant collagen I assembles in an altered extracellular matrix affecting mineralization and bone properties and partially accumulating inside the cells, leading to impaired trafficking and cellular stress.
A complete understanding of protein function and dynamics requires the characterization of the multiple thermodynamic states, including the denatured state ensemble (DSE). Whereas residual structure in the DSE (as well as in partially folded states) is pertinent in many biological contexts, here we are interested in how such structure affects protein thermodynamics. We examine issues related to chain collapse in light of new developments, focusing on potential complications arising from differences in the DSE's properties under various conditions.
Context: Pathogenic variants in the TBCE gene, encoding tubulin-specific chaperone E crucial for tubulin folding, are linked to three severe neurodevelopmental disorders: Hypoparathyroidism-retardation-dysmorphism (HRD) syndrome, Kenny-Caffey syndrome type 1, and progressive encephalopathy with amyotrophy and optic atrophy.
Objective: We identified patients with a novel, milder TBCE-associated phenotype and aimed to characterize it at the clinical and molecular levels.
Materials And Methods: We conducted splicing analysis using deep NGS sequencing of RT-PCR products and detected TBCE through Western blotting.
The oscillator of the cyanobacterial circadian clock relies on the ability of the KaiB protein to switch reversibly between a stable ground-state fold (gsKaiB) and an unstable fold-switched fold (fsKaiB). Rare fold-switching events by KaiB provide a critical delay in the negative feedback loop of this posttranslational oscillator. In this study, we experimentally and computationally investigate the temperature dependence of fold switching and its mechanism.
