Dataset Information

Heterochromatin Protein HP1? Gelation Dynamics Revealed by Solid-State NMR Spectroscopy.

ABSTRACT: Heterochromatin protein 1? (HP1?) undergoes liquid-liquid phase separation (LLPS) and forms liquid droplets and gels in?vitro, properties that also appear to be central to its biological function in heterochromatin compaction and regulation. Here we use solid-state NMR spectroscopy to track the conformational dynamics of phosphorylated HP1? during its transformation from the liquid to the gel state. Using experiments designed to probe distinct dynamic modes, we identify regions with varying mobilities within HP1? molecules and show that specific serine residues uniquely contribute to gel formation. The addition of chromatin disturbs the gelation process while preserving the conformational dynamics within individual bulk HP1? molecules. Our study provides a glimpse into the dynamic architecture of dense HP1? phases and showcases the potential of solid-state NMR to detect an elusive biophysical regime of phase separating biomolecules.

SUBMITTER: Ackermann BE

PROVIDER: S-EPMC6482055 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Heterochromatin Protein HP1α Gelation Dynamics Revealed by Solid-State NMR Spectroscopy.

Ackermann Bryce E BE Debelouchina Galia T GT

Angewandte Chemie (International ed. in English) 20190403 19

Heterochromatin protein 1α (HP1α) undergoes liquid-liquid phase separation (LLPS) and forms liquid droplets and gels in vitro, properties that also appear to be central to its biological function in heterochromatin compaction and regulation. Here we use solid-state NMR spectroscopy to track the conformational dynamics of phosphorylated HP1α during its transformation from the liquid to the gel state. Using experiments designed to probe distinct dynamic modes, we identify regions with varying mobi ...[more]

PMID: 30845353

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Project description:Rhodopsin is a canonical member of class A of the G protein-coupled receptors (GPCRs) that are implicated in many of the drug interventions in humans and are of great pharmaceutical interest. The molecular mechanism of rhodopsin activation remains unknown as atomistic structural information for the active metarhodopsin II state is currently lacking. Solid-state (2)H NMR constitutes a powerful approach to study atomic-level dynamics of membrane proteins. In the present application, we describe how information is obtained about interactions of the retinal cofactor with rhodopsin that change with light activation of the photoreceptor. The retinal methyl groups play an important role in rhodopsin function by directing conformational changes upon transition into the active state. Site-specific (2)H labels have been introduced into the methyl groups of retinal and solid-state (2)H NMR methods applied to obtain order parameters and correlation times that quantify the mobility of the cofactor in the inactive dark state, as well as the cryotrapped metarhodopsin I and metarhodopsin II states. Analysis of the angular-dependent (2)H NMR line shapes for selectively deuterated methyl groups of rhodopsin in aligned membranes enables determination of the average ligand conformation within the binding pocket. The relaxation data suggest that the beta-ionone ring is not expelled from its hydrophobic pocket in the transition from the pre-activated metarhodopsin I to the active metarhodopsin II state. Rather, the major structural changes of the retinal cofactor occur already at the metarhodopsin I state in the activation process. The metarhodopsin I to metarhodopsin II transition involves mainly conformational changes of the protein within the membrane lipid bilayer rather than the ligand. The dynamics of the retinylidene methyl groups upon isomerization are explained by an activation mechanism involving cooperative rearrangements of extracellular loop E2 together with transmembrane helices H5 and H6. These activating movements are triggered by steric clashes of the isomerized all-trans retinal with the beta4 strand of the E2 loop and the side chains of Glu(122) and Trp(265) within the binding pocket. The solid-state (2)H NMR data are discussed with regard to the pathway of the energy flow in the receptor activation mechanism.

Dataset Information

Heterochromatin Protein HP1? Gelation Dynamics Revealed by Solid-State NMR Spectroscopy.

Publications

Heterochromatin Protein HP1α Gelation Dynamics Revealed by Solid-State NMR Spectroscopy.

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