scholarly journals Site-specific Crosslinking Coupled with Mass Spectrometry as a Structural Tool in Studies of the Human α1 Glycine Receptor

2020 ◽  
Author(s):  
Rathna J. Veeramachaneni ◽  
Chelsee A. Donelan ◽  
Kayce A. Tomcho ◽  
Shaili Aggarwal ◽  
David J. Lapinsky ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Resting State ◽  
Glycine Receptor ◽  
Integral Membrane Protein ◽  
Cysteine Residue ◽  
Distance Constraints ◽  
State Dependent ◽  
Sds Page ◽  
Lipid Environment ◽  
Structural Methods

AbstractRecent advances in mass spectrometry coupled with chemical crosslinking (CX-MS) can be applied for the structural interrogation of macromolecular complexes to identify statedependent distance constraints and provides a powerful complementary technique to other structural methods. In this study, we develop a CX-MS approach to identify the sites of crosslinking from a single targeted location within the human glycine receptor (GlyR) in a single apo/resting state. The GlyR belongs to the family of pentameric ligand-gated ion channel receptors that function in fast neuronal transmission. A single cysteine residue was re-introduced into Cys null GlyR construct at position 41 within the extracellular domain of an overexpressed human a1 homomeric GlyR. After purification and reconstitution into vesicles, a methanethiosulfonate benzophenone heterobifunctional crosslinker was attached via formation of a disulfide bond, and the resting receptor is subsequently photocrosslinked. Monomeric and oligomeric bands from SDS-PAGE gels were then trypsinized and analyzed by tandem MS in bottom-up studies. Dozens of intra- and inter-subunit sites of crosslinking were differentiated and identified from single gel bands (pmols of purified GlyR), showing the utility of this approach to identify a diverse array of distance constraints of GlyR in its resting state. These studies highlight the potential of CX-MS as an experimental approach to identify state-dependent crosslinks of full length integral membrane protein assemblies in a native-like lipid environment.

scholarly journals State-dependent mapping of GlyR-cholesterol interactions by coupling crosslinking with mass spectrometry

2020 ◽  
Author(s):  
Nicholas A. Ferraro ◽  
Michael Cascio
Keyword(s):  
Mass Spectrometry ◽  
Lipid Bilayers ◽  
Glycine Receptor ◽  
Transmembrane Helix ◽  
Covalent Attachment ◽  
Channel Dynamics ◽  
State Dependent ◽  
Extracellular Region ◽  
Lipid Environment ◽  
And Function

AbstractPentameric ligand-gated ion channel (pLGIC) allostery is dependent on dynamic associations with its diverse environment. The cellular membrane’s lipid composition influences channel function with cholesterol being a key regulator of channel activity. Human α1 glycine receptor (GlyR) was purified from baculovirus infected insect cells and reconstituted in unilamellar vesicles at physiological cholesterol:lipid ratios with aliquots of azi-cholesterol, a photoactivatable non-specific crosslinker. The receptor in vesicles was then enriched in either a resting, open, or desensitized state prior to photocrosslinking. Following photoactivation, crosslinked cholesterol-GlyR was trypsinized and sites of direct covalent attachment to peptides were identified by targeted MS/MS. Dozens of state-dependent crosslinks were identified and differential patterns of cholesterol-GlyR crosslinks were observed in the extracellular region nearing the lipid bilayer, in the M4 transmembrane helix, and in the large intracellular M3-M4 loop. Unique crosslinks in comparative studies identify changes in lipid accessibility or modulation of hydrophobic cavities in GlyR as a function of receptor allostery. Most notably, the outward twisting of M4 and differential crosslinking within the M3-M4 loop provide new insight into allosteric repositioning of GlyR. More generally, this study provides an accurate and sensitive approach to mapping the protein-lipid interactions to discern state-dependent structural movements of membrane proteins embedded in lipid-bilayers.SignificanceIon channels are highly allosteric molecular machines whose structure and function are sensitive to lipids and ligands. While the structures of many pLGICs are known, these are often truncated forms of the receptor in a membrane-mimetic environment locked in ligand-bound conformational states that may not accurately reflect the conformation and dynamics of the receptor in a native lipid environment. Crosslinking coupled with mass spectrometry (CX-MS) has the capability of interrogating the structure of full-length receptors in a lipid environment. In this study, CX-MS was used to identify state-dependent cholesterol-GlyR interactions to identify differential cholesterol accessibility as a function of channel dynamics upon gating and desensitization.

scholarly journals Targeted State Dependent Crosslinking Mass Spectrometry (CXMS) of the Human Alpha 1 Glycine Receptor (GLyR)

2019 ◽  
Vol 116 (3) ◽  
pp. 392a
Author(s):  
Kayce A. Tomcho ◽  
Hannah E. Gering ◽  
Rathna J. Veeramachaneni ◽  
David J. Lapinsky ◽  
Michael Cascio
Keyword(s):  
Mass Spectrometry ◽  
Glycine Receptor ◽  
State Dependent

Statistical Force-Field for Structural Modeling Using Chemical Cross-Linking/mass Spectrometry Distance Constraints

2018 ◽  
Author(s):  
Allan J. R. Ferrari ◽  
Fabio C. Gozzo ◽  
Leandro Martinez
Keyword(s):  
Mass Spectrometry ◽  
Amino Acid ◽  
Force Field ◽  
Protein Structures ◽  
Protein Structure Determination ◽  
Structural Modeling ◽  
Cross Linking ◽  
Amino Acid Residues ◽  
Distance Constraints ◽  
Chemical Cross Linking

<div><p>Chemical cross-linking/Mass Spectrometry (XLMS) is an experimental method to obtain distance constraints between amino acid residues, which can be applied to structural modeling of tertiary and quaternary biomolecular structures. These constraints provide, in principle, only upper limits to the distance between amino acid residues along the surface of the biomolecule. In practice, attempts to use of XLMS constraints for tertiary protein structure determination have not been widely successful. This indicates the need of specifically designed strategies for the representation of these constraints within modeling algorithms. Here, a force-field designed to represent XLMS-derived constraints is proposed. The potential energy functions are obtained by computing, in the database of known protein structures, the probability of satisfaction of a topological cross-linking distance as a function of the Euclidean distance between amino acid residues. The force-field can be easily incorporated into current modeling methods and software. In this work, the force-field was implemented within the Rosetta ab initio relax protocol. We show a significant improvement in the quality of the models obtained relative to current strategies for constraint representation. This force-field contributes to the long-desired goal of obtaining the tertiary structures of proteins using XLMS data. Force-field parameters and usage instructions are freely available at http://m3g.iqm.unicamp.br/topolink/xlff <br></p></div><p></p><p></p>

scholarly journals Effect of Ocular Hypertension on D-β-Aspartic Acid-Containing Proteins in the Retinas of Rats

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Takashi Kanamoto ◽  
Takashi Tachibana ◽  
Yasushi Kitaoka ◽  
Toshio Hisatomi ◽  
Yasuhiro Ikeda ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Ocular Hypertension ◽  
Aspartic Acid ◽  
Atp Synthase ◽  
Wistar Rats ◽  
Protein Band ◽  
Mass Spectrometry Analysis ◽  
Liquid Chromatography Mass Spectrometry ◽  
Spectrometry Analysis ◽  
Sds Page

Purpose. To investigate the effect of ocular hypertension-induced isomerization of aspartic acid in retinal proteins. Methods. Adult Wistar rats with ocular hypertension were used as an experimental model. D-β-aspartic acid-containing proteins were isolated by SDS-PAGE and western blot with an anti-D-β-aspartic acid antibody and identified by liquid chromatography-mass spectrometry analysis. The concentration of ATP was measured by ELISA. Results. D-β-aspartic acid was expressed in a protein band at around 44.5 kDa at much higher quantities in the retinas of rats with ocular hypertension than in those of normotensive rats. The 44.5 kDa protein band was mainly composed of α-enolase, S-arrestin, and ATP synthase subunits α and β, in both the ocular hypertensive and normotensive retinas. Moreover, increasing intraocular pressure was correlated with increasing ATP concentrations in the retinas of rats. Conclusion. Ocular hypertension affected the expression of proteins containing D-β-aspartic acid, including ATP synthase subunits, and up-regulation of ATP in the retinas of rats.

Application of 2D BN/SDS-PAGE coupled with mass spectrometry for identification of VDAC-associated protein complexes related to mitochondrial binding sites for type I brain hexokinase

Mitochondrion ◽  
2013 ◽  
Vol 13 (6) ◽  
pp. 823-830 ◽  
Author(s):  
Carla Rossini Crepaldi ◽  
Phelipe Augusto Mariano Vitale ◽  
Andrea Cristina Tesch ◽  
Hélen Julie Laure ◽  
José César Rosa ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Binding Sites ◽  
Protein Complexes ◽  
Type I ◽  
Sds Page

scholarly journals Labile disulfide bonds are common at the leucocyte cell surface

Open Biology ◽  
2011 ◽  
Vol 1 (3) ◽  
pp. 110010 ◽  
Author(s):  
Clive Metcalfe ◽  
Peter Cresswell ◽  
Laura Ciaccia ◽  
Benjamin Thomas ◽  
A. Neil Barclay
Keyword(s):  
Mass Spectrometry ◽  
Membrane Proteins ◽  
Cell Surface ◽  
Disulfide Bonds ◽  
Reduction Process ◽  
Cysteine Residue ◽  
Surface Proteins ◽  
Protein Activity ◽  
Functional Changes ◽  
Reducing Conditions

Redox conditions change in events such as immune and platelet activation, and during viral infection, but the biochemical consequences are not well characterized. There is evidence that some disulfide bonds in membrane proteins are labile while others that are probably structurally important are not exposed at the protein surface. We have developed a proteomic/mass spectrometry method to screen for and identify non-structural, redox-labile disulfide bonds in leucocyte cell-surface proteins. These labile disulfide bonds are common, with several classes of proteins being identified and around 30 membrane proteins regularly identified under different reducing conditions including using enzymes such as thioredoxin. The proteins identified include integrins, receptors, transporters and cell–cell recognition proteins. In many cases, at least one cysteine residue was identified by mass spectrometry as being modified by the reduction process. In some cases, functional changes are predicted (e.g. in integrins and cytokine receptors) but the scale of molecular changes in membrane proteins observed suggests that widespread effects are likely on many different types of proteins including enzymes, adhesion proteins and transporters. The results imply that membrane protein activity is being modulated by a ‘redox regulator’ mechanism.

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