25-30 August 2019
Henry Ford Building
Europe/Berlin timezone

A generalized approach for NMR studies of lipid–protein interactions based on sparse fluorination of acyl chains

26 Aug 2019, 17:15
25m
Lecture Hall C (Henry Ford Building)

Lecture Hall C

Henry Ford Building

Talk Biological applications Biomolecules

Speaker

Dr Tammo Diercks (CiC bioGUNE)

Description

High-resolution NMR studies on protein-lipid interactions are severely limited by poor 1H signal dispersion in the lipids' acyl chains, where uniform 13C enrichment cannot resolve all overlap problems and introduces no distinct molecular marker from a likewise 13C enriched protein to separate inter- from intramolecular NOE signals. We present a new approach [1] that relies on sparse fluorination of lipid acyl chains and exploits fluorine both indirectly, as a shift reagent affecting nearby spins, and directly, as a distinctive isotope (19F) with superb NMR properties. The introduced fluorine atoms then solve the NMR resolution problem for acyl chains by (i) increasing their 1H signal dispersion via local deshielding, (ii) enabling clean molecular distinction via 19F filtering, and (iii) allowing further resolution enhancement via 19F editing. While the number of H/F substitutions must be minimised to mitigate any biophysical impact, prevent complications from 1JFF coupling, and preserve a high 1Hlipid density to probe intermolecular contacts via 1Hlipid-1Hprotein NOE signals, a minimal fluorination scheme is defined by the reach of fluorine induced deshielding and JHF coupling. We, thus, designed di-(4-fluoro)heptanoyl¬phosphocholine (4F-DHPC7) that forms stable micelles with similar size as DHPC7, but with fully dispersed high-resolution 1H and 19F spectra. Both DHPC7 and 4F-DHPC7 micelles readily stabilise the phototaxis receptor sensory rhodopsin II (pSRII) and outer membrane protein X (OmpX), where 15N TROSY signals differ notably only for residues near the fluorine atoms in modelled 4F-DHPC7 micelles. Thus, H/F substitution in lipid chains also causes localised fluorine induced chemical shift perturbations (CSPF) in solubilised proteins, indicating their lipid layer insertion similar to paramagnetic markers, but with minimal steric impact and finer distance resolution. Finally, a first 19F filtered NOESY spectrum unambiguously brought out intermolecular contacts between 4F-DHPC7 and a bihelical integrin fragment.
[1] De Biasio et al, Chem.Comm. (2018) 54, 7306-7309

Primary authors

Dr Tammo Diercks (CiC bioGUNE) Dr Francisco J. Blanco (CiC bioGUNE) Dr Alfredo De Biasio (University of Leicester) Dr Alain Ibañez de Opacua (Max Planck Institute for Biophysical Chemistry) Prof. Daniel Nietlispach (University of Cambridge (UK)) Dr Mark J. Bostock (University of Cambridge)

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