Transmembrane Protein Activation Refined by Site‐Specific Hydration Dynamics

Hussain, Sarah; Franck, John M.; Han, Songi

doi:10.1002/anie.201206147

Cited by 50 publications

(68 citation statements)

References 51 publications

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“…Overhauser DNP results for spin-labeled membrane proteins [18,19], but this has not yet been carried out. However, diffusion constants of water in the vicinity of MTSL spin labels and native amino acids have been investigated in an earlier MD study [86].…”

Section: Dynamics Of Spin Labels and Relaxationmentioning

confidence: 99%

“…Such SDSL techniques are widely applied in PRE studies. They have also been used in recent liquidstate DNP work [18,19], and may become attractive for solid-state DNP [20]. Once a protein or nucleic acid is spin labeled, further information can be obtained from CW EPR experiments [14] or distance measurements between spin labels by pulsed EPR techniques [21].…”

Section: Introductionmentioning

confidence: 99%

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Conformational dynamics and distribution of nitroxide spin labels

Jeschke

2013

Progress in Nuclear Magnetic Resonance Spectroscopy

137

115

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Long-range distance measurements based on paramagnetic relaxation enhancement (PRE) in NMR, quantification of surface water dynamics near biomacromolecules by Overhauser dynamic nuclear polarization (DNP) and sensitivity enhancement by solid-state DNP all depend on introducing paramagnetic species into an otherwise diamagnetic NMR sample. The species can be introduced by site-directed spin labeling, which offers precise control for positioning the label in the sequence of a biopolymer. However, internal flexibility of the spin label gives rise to dynamic processes that potentially influence PRE and DNP behavior and leads to a spatial distribution of the electron spin even in solid samples. Internal dynamics of spin labels and their static conformational distributions have been studied mainly by electron paramagnetic resonance spectroscopy and molecular dynamics simulations, with a large body of results for the most widely applied methanethiosulfonate spin label MTSL. These results are critically discussed in a unifying picture based on rotameric states of the group that carries the spin label. Deficiencies in our current understanding of dynamics and conformations of spin labeled groups and of their influence on NMR observables are highlighted and directions for further research suggested.

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Section: Dynamics Of Spin Labels and Relaxationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Conformational dynamics and distribution of nitroxide spin labels

Jeschke

2013

Progress in Nuclear Magnetic Resonance Spectroscopy

137

115

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“…61,62,69 Typically, the hydration dynamics at several ns or longer timescales is contributed from bound water, whereas hydration dynamics at ps timescale is contributed from loosely bound and freely diffusing water at or near molecular interfaces. This analysis is model-independent and permits the direct comparison of different classes of hydration waters in different local environments.…”

Section: −1mentioning

confidence: 99%

Cholesterol enhances surface water diffusion of phospholipid bilayers

Cheng

Olijve

Kausik

et al. 2014

The Journal of Chemical Physics

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Elucidating the physical effect of cholesterol (Chol) on biological membranes is necessary towards rationalizing their structural and functional role in cell membranes. One of the debated questions is the role of hydration water in Chol-embedding lipid membranes, for which only little direct experimental data are available. Here, we study the hydration dynamics in a series of Chol-rich and depleted bilayer systems using an approach termed 1 H Overhauser dynamic nuclear polarization (ODNP) NMR relaxometry that enables the sensitive and selective determination of water diffusion within 5-10 Å of a nitroxide-based spin label, positioned off the surface of the polar headgroups or within the nonpolar core of lipid membranes. The Chol-rich membrane systems were prepared from mixtures of Chol, dipalmitoyl phosphatidylcholine and/or dioctadecyl phosphatidylcholine lipid that are known to form liquid-ordered, raft-like, domains. Our data reveal that the translational diffusion of local water on the surface and within the hydrocarbon volume of the bilayer is significantly altered, but in opposite directions: accelerated on the membrane surface and dramatically slowed in the bilayer interior with increasing Chol content. Electron paramagnetic resonance (EPR) lineshape analysis shows looser packing of lipid headgroups and concurrently tighter packing in the bilayer core with increasing Chol content, with the effects peaking at lipid compositions reported to form lipid rafts. The complementary capability of ODNP and EPR to site-specifically probe the hydration dynamics and lipid ordering in lipid membrane systems extends the current understanding of how Chol may regulate biological processes. One possible role of Chol is the facilitation of interactions between biological constituents and the lipid membrane through the weakening or disruption of strong hydrogen-bond networks of the surface hydration layers that otherwise exert stronger repulsive forces, as reflected in faster surface water diffusivity. Another is the concurrent tightening of lipid packing that reduces passive, possibly unwanted, diffusion of ions and water across the bilayer.

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“…The spin labeling approach presented here is able to probe a functionally relevant loop region that undergoes a major conformational transformation upon light activation (residue 177 on the E-F loop) (Hussain et al, 2013) but cannot be resolved in most crystal structures given its dynamic nature (Columbus and Hubbell, 2002). Unlike crystallography, PDS also confers the capability to probe distances in a variety of membrane-mimetic surfactant conditions that may alter the oligomeric distribution and interprotein packing (Georgieva et al, 2013;Hä nelt et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

“…An increased width of r 2 with respect to r 1 is also consistent with the experimental results obtained with 58G1. The solvent-exposed label at site Thr177 is intrinsically more flexible (Hussain et al, 2013), leading to significantly broader distributions of distances (z1.5 nm FWHM) with maxima at 4.0 and 7.0 nm. Here the nonsymmetric model showed better agreement with the experimental results than the symmetric one.…”

Section: Structural Modelingmentioning

confidence: 99%

Determining the Oligomeric Structure of Proteorhodopsin by Gd3+-Based Pulsed Dipolar Spectroscopy of Multiple Distances

et al. 2014

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The structural organization of the functionally relevant, hexameric oligomer of green-absorbing proteorhodopsin (G-PR) was obtained from double electron-electron resonance (DEER) spectroscopy utilizing conventional nitroxide spin labels and recently developed Gd3+ -based spin labels. G-PR with nitroxide or Gd3+ labels was prepared using cysteine mutations at residues Trp58 and Thr177. By combining reliable measurements of multiple interprotein distances in the G-PR hexamer with computer modeling, we obtained a structural model that agrees with the recent crystal structure of the homologous blue-absorbing PR (B-PR) hexamer. These DEER results provide specific distance information in a membrane-mimetic environment and across loop regions that are unresolved in the crystal structure. In addition, the X-band DEER measurements using nitroxide spin labels suffered from multispin effects that, at times, compromised the detection of next-nearest neighbor distances. Performing measurements at high magnetic fields with Gd3+ spin labels increased the sensitivity considerably and alleviated the difficulties caused by multispin interactions.

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Transmembrane Protein Activation Refined by Site‐Specific Hydration Dynamics

Cited by 50 publications

References 51 publications

Conformational dynamics and distribution of nitroxide spin labels

Conformational dynamics and distribution of nitroxide spin labels

Cholesterol enhances surface water diffusion of phospholipid bilayers

Determining the Oligomeric Structure of Proteorhodopsin by Gd3+-Based Pulsed Dipolar Spectroscopy of Multiple Distances

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