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Alpízar-Pedraza D, Roque-Diaz Y, Garay-Pérez H, Rosenau F, Ständker L, Montero-Alejo V. Insights into the Adsorption Mechanisms of the Antimicrobial Peptide CIDEM-501 on Membrane Models. Antibiotics (Basel) 2024; 13:167. [PMID: 38391553 PMCID: PMC10886324 DOI: 10.3390/antibiotics13020167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 02/02/2024] [Accepted: 02/05/2024] [Indexed: 02/24/2024] Open
Abstract
CIDEM-501 is a hybrid antimicrobial peptide rationally designed based on the structure of panusin and panulirin template peptides. The new peptide exhibits significant antibacterial activity against multidrug-resistant pathogens (MIC = 2-4 μM) while conserving no toxicity in human cell lines. We conducted molecular dynamics (MD) simulations using the CHARMM-36 force field to explore the CIDEM-501 adsorption mechanism with different membrane compositions. Several parameters that characterize these interactions were analyzed to elucidate individual residues' structural and thermodynamic contributions. The membrane models were constructed using CHARMM-GUI, mimicking the bacterial and eukaryotic phospholipid compositions. Molecular dynamics simulations were conducted over 500 ns, showing rapid and highly stable peptide adsorption to bacterial lipids components rather than the zwitterionic eucaryotic model membrane. A predominant peptide orientation was observed in all models dominated by an electric dipole. The peptide remained parallel to the membrane surface with the center loop oriented to the lipids. Our findings shed light on the antibacterial activity of CIDEM-501 on bacterial membranes and yield insights valuable for designing potent antimicrobial peptides targeting multi- and extreme drug-resistant bacteria.
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Affiliation(s)
- Daniel Alpízar-Pedraza
- Biochemistry and Molecular Biology Department, Center for Pharmaceutical Research and Development, Ave. 26 # 1605, Nuevo Vedado, Ciudad de La Habana 10400, Cuba
| | - Yessica Roque-Diaz
- Biochemistry and Molecular Biology Department, Center for Pharmaceutical Research and Development, Ave. 26 # 1605, Nuevo Vedado, Ciudad de La Habana 10400, Cuba
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Via Brecce Bianche, 12, 60131 Ancona, Italy
| | - Hilda Garay-Pérez
- Peptide Synthesis Group, Center for Genetic Engineering and Biotechnology, Ave. 31 e/158 y 190, Playa, Habana 11600, Cuba
| | - Frank Rosenau
- Institute of Pharmaceutical Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Ludger Ständker
- Core Facility for Functional Peptidomics, Ulm Peptide Pharmaceuticals (U-PEP), Faculty of Medicine, Ulm University, 89081 Ulm, Germany
| | - Vivian Montero-Alejo
- Biochemistry and Molecular Biology Department, Center for Pharmaceutical Research and Development, Ave. 26 # 1605, Nuevo Vedado, Ciudad de La Habana 10400, Cuba
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2
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Mildenberger V, Alpízar-Pedraza D, Martell-Huguet EM, Krämer M, Bolotnikov G, Otero-Gonzalez AJ, Weil T, Rodriguez-Alfonso A, Preising N, Ständker L, Vogel V, Spellerberg B, Kissmann AK, Rosenau F. The Designed Pore-Forming Antimicrobial Peptide C14R Combines Excellent Activity against the Major Opportunistic Human Pathogen Pseudomonas aeruginosa with Low Cytotoxicity. Pharmaceuticals (Basel) 2024; 17:83. [PMID: 38256916 PMCID: PMC10820675 DOI: 10.3390/ph17010083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 12/21/2023] [Accepted: 01/05/2024] [Indexed: 01/24/2024] Open
Abstract
The diminishing portfolio of mankind's available antibiotics urges science to develop novel potent drugs. Here, we present a peptide fitting the typical blueprint of amphipathic and membrane-active antimicrobial peptides, denominated C14R. This 2 kDa peptide consists of 16 amino acid residues, with seven being either hydrophobic, aromatic, or non-polar, and nine being polar or positively charged, strictly separated on opposite sides of the predicted α-helix. The affinity of the peptide C14R to P. aeruginosa membranes and its intrinsic tendency to productively insert into membranes of such composition were analyzed by dynamic simulations. Its biological impact on the viability of two different P. aeruginosa reference strains was demonstrated by determining the minimal inhibitory concentrations (MICs), which were found to be in the range of 10-15 µg/mL. C14R's pore-forming capability was verified in a permeabilization assay based on the peptide-triggered uptake of fluorescent dyes into the bacterial cells. Finally, the peptide was used in radial diffusion assays, which are commonly used for susceptibility testing of antimicrobial peptides in clinical microbiology. In comparison to reference strains, six clinical P. aeruginosa isolates were clearly affected, thereby paving the way for further in-depth analyses of C14R as a promising new AMP drug in the future.
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Affiliation(s)
- Vanessa Mildenberger
- Institute of Pharmaceutical Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (V.M.); (M.K.); (G.B.)
| | - Daniel Alpízar-Pedraza
- Center for Pharmaceutical Research and Development (CIDEM), 26th Avenue, No. 1605, Nuevo Vedado, La Habana 10400, Cuba;
| | - Ernesto M. Martell-Huguet
- Center for Protein Studies, Faculty of Biology, University of Havana, 25 and I, La Habana 10400, Cuba; (E.M.M.-H.); (A.J.O.-G.)
| | - Markus Krämer
- Institute of Pharmaceutical Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (V.M.); (M.K.); (G.B.)
| | - Grigory Bolotnikov
- Institute of Pharmaceutical Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (V.M.); (M.K.); (G.B.)
| | - Anselmo J. Otero-Gonzalez
- Center for Protein Studies, Faculty of Biology, University of Havana, 25 and I, La Habana 10400, Cuba; (E.M.M.-H.); (A.J.O.-G.)
| | - Tanja Weil
- Max Planck Institute for Polymer Research Mainz, Ackermannweg 10, 55128 Mainz, Germany;
| | - Armando Rodriguez-Alfonso
- Core Facility for Functional Peptidomics (CFP), Faculty of Medicine, Ulm University, 89081 Ulm, Germany; (A.R.-A.); (N.P.); (L.S.)
- Core Unit of Mass Spectrometry and Proteomics, Faculty of Medicine, Ulm University, 89081 Ulm, Germany
| | - Nico Preising
- Core Facility for Functional Peptidomics (CFP), Faculty of Medicine, Ulm University, 89081 Ulm, Germany; (A.R.-A.); (N.P.); (L.S.)
| | - Ludger Ständker
- Core Facility for Functional Peptidomics (CFP), Faculty of Medicine, Ulm University, 89081 Ulm, Germany; (A.R.-A.); (N.P.); (L.S.)
| | - Verena Vogel
- Institute of Medical Microbiology and Hygiene, University Clinic of Ulm, TBC1 Forschung, Albert-Einstein-Allee 11, 89081 Ulm, Germany (B.S.)
| | - Barbara Spellerberg
- Institute of Medical Microbiology and Hygiene, University Clinic of Ulm, TBC1 Forschung, Albert-Einstein-Allee 11, 89081 Ulm, Germany (B.S.)
| | - Ann-Kathrin Kissmann
- Institute of Pharmaceutical Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (V.M.); (M.K.); (G.B.)
- Max Planck Institute for Polymer Research Mainz, Ackermannweg 10, 55128 Mainz, Germany;
| | - Frank Rosenau
- Institute of Pharmaceutical Biotechnology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (V.M.); (M.K.); (G.B.)
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3
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Oleynikov IP, Sudakov RV, Radyukhin VA, Arutyunyan AM, Azarkina NV, Vygodina TV. Interaction of Amphipathic Peptide from Influenza Virus M1 Protein with Mitochondrial Cytochrome Oxidase. Int J Mol Sci 2023; 24:ijms24044119. [PMID: 36835528 PMCID: PMC9961948 DOI: 10.3390/ijms24044119] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 02/07/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
The Bile Acid Binding Site (BABS) of cytochrome oxidase (CcO) binds numerous amphipathic ligands. To determine which of the BABS-lining residues are critical for interaction, we used the peptide P4 and its derivatives A1-A4. P4 is composed of two flexibly bound modified α-helices from the M1 protein of the influenza virus, each containing a cholesterol-recognizing CRAC motif. The effect of the peptides on the activity of CcO was studied in solution and in membranes. The secondary structure of the peptides was examined by molecular dynamics, circular dichroism spectroscopy, and testing the ability to form membrane pores. P4 was found to suppress the oxidase but not the peroxidase activity of solubilized CcO. The Ki(app) is linearly dependent on the dodecyl-maltoside (DM) concentration, indicating that DM and P4 compete in a 1:1 ratio. The true Ki is 3 μM. The deoxycholate-induced increase in Ki(app) points to a competition between P4 and deoxycholate. A1 and A4 inhibit solubilized CcO with Ki(app)~20 μM at 1 mM DM. A2 and A3 hardly inhibit CcO either in solution or in membranes. The mitochondrial membrane-bound CcO retains sensitivity to P4 and A4 but acquires resistance to A1. We associate the inhibitory effect of P4 with its binding to BABS and dysfunction of the proton channel K. Trp residue is critical for inhibition. The resistance of the membrane-bound enzyme to inhibition may be due to the disordered secondary structure of the inhibitory peptide.
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4
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Pal S, Koeppe RE, Chattopadhyay A. Membrane electrostatics sensed by tryptophan anchors in hydrophobic model peptides depends on non-aromatic interfacial amino acids: implications in hydrophobic mismatch. Faraday Discuss 2021; 232:330-346. [PMID: 34549729 DOI: 10.1039/d0fd00065e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
WALPs are synthetic α-helical membrane-spanning peptides that constitute a well-studied system for exploring hydrophobic mismatch. These peptides represent a simplified consensus motif for transmembrane domains of intrinsic membrane proteins due to their hydrophobic core of alternating leucine and alanine flanked by membrane-anchoring aromatic tryptophan residues. Although the modulation of mismatch responses in WALPs by tryptophan anchors has been reported earlier, there have been limited attempts to utilize the intrinsic tryptophan fluorescence of this class of peptides in mismatch sensors. We have previously shown, utilizing the red edge excitation shift (REES) approach, that interfacial WALP tryptophan residues in fluid phase bilayers experience a dynamically constrained membrane microenvironment. Interestingly, emerging reports suggest the involvement of non-aromatic interfacially localized residues in modulating local structure and dynamics in WALP analogs. In this backdrop, we have explored the effect of interfacial amino acids, such as lysine (in KWALPs) and glycine (in GWALPs), on the tryptophan microenvironment of WALP analogs in zwitterionic and negatively charged membranes. We show that interfacial tryptophans in KWALP and GWALP experience a more restricted microenvironment, as reflected in the substantial increase in magnitude of REES and apparent rotational correlation time, relative to those in WALP in zwitterionic membranes. Interestingly, in contrast to WALP, the tryptophan anchors in KWALP and GWALP appear insensitive to the presence of negatively charged lipids in the membrane. These results reveal a subtle interplay between non-aromatic flanking residues in transmembrane helices and negatively charged lipids at the membrane interface, which could modulate the membrane microenvironment experienced by interfacially localized tryptophan residues. Since interfacial tryptophans are known to influence mismatch responses in WALPs, our results highlight the possibility of utilizing the fluorescence signatures of tryptophans in membrane proteins or model peptides such as WALP as markers for assessing protein responses to hydrophobic mismatch. More importantly, these results constitute one of the first reports on the influence of lipid headgroup charge in fine-tuning hydrophobic mismatch in membrane bilayers, thereby enriching the existing framework of hydrophobic mismatch.
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Affiliation(s)
- Sreetama Pal
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500 007, India. .,CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India.,Academy of Scientific and Innovative Research, Ghaziabad 201 002, India
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, AR 72701, USA
| | - Amitabha Chattopadhyay
- CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500 007, India. .,Academy of Scientific and Innovative Research, Ghaziabad 201 002, India
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5
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Price JR, Afrose F, Greathouse DV, Koeppe RE. Illuminating Disorder Induced by Glu in a Stable Arg-Anchored Transmembrane Helix. ACS OMEGA 2021; 6:20611-20618. [PMID: 34396006 PMCID: PMC8359125 DOI: 10.1021/acsomega.1c02800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 07/13/2021] [Indexed: 06/13/2023]
Abstract
Membrane proteins are vital for biological function and are complex to study. Even in model peptide-lipid systems, the combined influence or interaction of pairs of chemical groups still is not well understood. Disordered proteins, whether in solution or near lipid membranes, are an emerging paradigm for the initiation and control of biological function. The disorder can involve molecular orientation as well as molecular folding. This paper reports an astonishing induction of disorder when one Glu residue is introduced into a highly stable 23-residue transmembrane helix. The parent helix is anchored by a single Arg residue, tilted at a well-defined angle with respect to the DOPC bilayer normal and undergoes rapid cone precession. When Glu is introduced two residues away from Arg, with 200° (or 160°) radial separation, the helix properties change radically to exhibit a multiplicity of three or more disordered states. The helix characteristics have been monitored by deuterium (2H) NMR spectroscopy as functions of the pH and lipid bilayer composition. The disordered multistate behavior of the (Glu, Arg)-containing helix varies with the lipid bilayer thickness and pH. The results highlight a fundamental induction of protein multistate properties by a single Glu residue in a lipid membrane environment.
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6
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McKay M, Marr KA, Price JR, Greathouse DV, Koeppe RE. Lipid-Dependent Titration of Glutamic Acid at a Bilayer Membrane Interface. ACS OMEGA 2021; 6:8488-8494. [PMID: 33817510 PMCID: PMC8015139 DOI: 10.1021/acsomega.1c00276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 03/08/2021] [Indexed: 06/12/2023]
Abstract
The ionization properties of protein side chains in lipid-bilayer membranes will differ from the canonical values of side chains exposed to an aqueous solution. While the propensities of positively charged side chains of His, Lys, and Arg to release a proton in lipid membranes have been rather well characterized, the propensity for a negatively charged Glu side chain to receive a proton and achieve the neutral state in a bilayer membrane has been less well characterized. Indeed, the ionization of the glutamic acid side chain has been predicted to depend on its depth of burial in a lipid membrane but has been difficult to verify experimentally. To address the issue, we incorporated an interfacial Glu residue at position 4 of a distinct 23-residue transmembrane helix and used 2H NMR to examine the helix properties as a function of pH. We observe that the helix tilt and azimuthal rotation vary little with pH, but the extent of helix unraveling near residues 3 and 4 changes as the Glu residue E4 titrates. Remarkably, the 2H quadrupolar splitting for the side chain of alanine A3 responds to pH with an apparent pK a of 4.8 in 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) and 6.3 in 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC), but is unchanged up to pH 8.0 in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in the presence of residue E4. With bilayers composed of alkali-stable ether-linked lipids, the side chain of A3 responds to pH with an apparent pK a of 11.0 in the ether analogue of DOPC. These results suggest that the depth dependence of Glu ionization in lipid-bilayer membranes may be steeper than previously predicted or envisioned.
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7
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Afrose F, Martfeld AN, Greathouse DV, Koeppe RE. Examination of pH dependency and orientation differences of membrane spanning alpha helices carrying a single or pair of buried histidine residues. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1863:183501. [PMID: 33130099 DOI: 10.1016/j.bbamem.2020.183501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 10/22/2020] [Accepted: 10/23/2020] [Indexed: 01/08/2023]
Abstract
We have employed the peptide framework of GWALP23 (acetyl-GGALWLALALALALALALWLAGA-amide) to examine the orientation, dynamics and pH dependence of peptides having buried single or pairs of histidine residues. When residue L8 is substituted to yield GWALP23-H8, acetyl-GGALWLAH8ALALALALALWLAGA-amide, the deuterium NMR spectra of 2H-labeled core alanine residues reveal a helix that occupies a single transmembrane orientation in DLPC, or in DMPC at low pH, yet shows multiple states at higher pH or in bilayers of DOPC. Moreover, a single histidine at position 8 or 16 in the GWALP23 framework is sensitive to pH. Titration points are observed near pH 3.5 for the deprotonation of H8 in lipid bilayers of DLPC or DMPC, and for H16 in DOPC. When residues L8 and L16 both are substituted to yield GWALP23-H8,16, the 2H NMR spectra show, interestingly, no titration dependence from pH 2-8, yet bilayer thickness-dependent orientation differences. The helix with H8 and H16 is found to adopt a transmembrane orientation in thin bilayers of DLPC, a combination of transmembrane and surface orientations in DMPC, and then a complete transition to a surface bound orientation in the thicker DPoPC and DOPC lipid bilayers. In the surface orientations, alanine A7 no longer fits within the core helix. These results along with previous studies with different locations of histidine residues suggest that lipid hydrophobic thickness is a first determinant and pH a second determinant for the helical orientation, along with possible side-chain snorkeling, when the His residues are incorporated into the hydrophobic region of a lipid membrane-associated helix.
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Affiliation(s)
- Fahmida Afrose
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Ashley N Martfeld
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Denise V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
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McKay MJ, Greathouse DV, Koeppe RE. Flanking aromatic residue competition influences transmembrane peptide helix dynamics. FEBS Lett 2020; 594:4280-4291. [DOI: 10.1002/1873-3468.13926] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/31/2020] [Accepted: 09/02/2020] [Indexed: 01/18/2023]
Affiliation(s)
- Matthew J. McKay
- Department of Chemistry and Biochemistry University of Arkansas Fayetteville AR USA
| | - Denise V. Greathouse
- Department of Chemistry and Biochemistry University of Arkansas Fayetteville AR USA
| | - Roger E. Koeppe
- Department of Chemistry and Biochemistry University of Arkansas Fayetteville AR USA
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9
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Comparing Interfacial Trp, Interfacial His and pH Dependence for the Anchoring of Tilted Transmembrane Helical Peptides. Biomolecules 2020; 10:biom10020273. [PMID: 32053887 PMCID: PMC7072424 DOI: 10.3390/biom10020273] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 02/07/2020] [Accepted: 02/10/2020] [Indexed: 11/27/2022] Open
Abstract
Charged and aromatic amino acid residues, being enriched toward the terminals of membrane-spanning helices in membrane proteins, help to stabilize particular transmembrane orientations. Among them, histidine is aromatic and can be positively charge at low pH. To enable investigations of the underlying protein-lipid interactions, we have examined the effects of single or pairs of interfacial histidine residues using the constructive low-dynamic GWALP23 (acetyl-GG2ALW5LALALALALALALW19LAG22A-amide) peptide framework by incorporating individual or paired histidines at locations 2, 5, 19 or 22. Analysis of helix orientation by means of solid-state 2H NMR spectra of labeled alanine residues reveals marked differences with H2,22 compared to W2,22. Nevertheless, the properties of membrane-spanning H2,22WALP23 helices show little pH dependence and are similar to those having Gly, Arg or Lys at positions 2 and 22. The presence of H5 or H19 influences the helix rotational preference but not the tilt magnitude. H5 affects the helical integrity, as residue 7 unwinds from the core helix; yet once again the helix orientation and dynamic properties show little sensitivity to pH. The overall results reveal that the detailed properties of transmembrane helices depend upon the precise locations of interfacial histidine residues.
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10
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Influence of interfacial tryptophan residues on an arginine-flanked transmembrane helix. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183134. [PMID: 31738898 DOI: 10.1016/j.bbamem.2019.183134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 10/31/2019] [Accepted: 11/01/2019] [Indexed: 10/25/2022]
Abstract
The transmembrane helices of membrane proteins often are flanked by interfacial charged or aromatic residues that potentially help to anchor the membrane-spanning protein. For isolated single-span helices, the interfacial residues may be especially important for stabilizing particular tilted transmembrane orientations. The peptide RWALP23 (acetyl-GR2ALW(LA)6LWLAR22A-amide) has been employed to investigate the interplay between interfacial arginines and tryptophans. Here we replace the tryptophans of RWALP23 with A5 and A19, to investigate arginines alone with respect to helix fraying and orientation in varying lipid bilayers. Deuterated alanines incorporated into the central sequence allow the orientation and stability of the core helix to be assessed by means of solid -state 2H NMR in bilayers of DOPC, DMPC and DLPC. The helix tilt from the bilayer normal is found to increase slightly when R2 and R22 are present, and increases still further when the tryptophans W5 and W19 are replaced by alanines. The extent of helix dynamic averaging remains low in all cases. The preferred helix azimuthal rotation is essentially constant for all of the helices in each of the lipid membranes considered here. The alanines located outside of the core region of the peptide are sensitive to helical integrity. The new alanines, A5 and A19, therefore, provide new information about the length of the core helix and the onset of unraveling of the terminals. Residue A19 remains essentially on the central helix in each lipid membrane, while residues A3, A5 and A21 deviate from the core helix to an extent that depends on the membrane thickness. Differential unraveling of the two ends to expose peptide backbone groups for hydrogen bonding therefore acts together with specific interfacial side chains to stabilize a transmembrane helix.
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11
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Kubyshkin V, Grage SL, Ulrich AS, Budisa N. Bilayer thickness determines the alignment of model polyproline helices in lipid membranes. Phys Chem Chem Phys 2019; 21:22396-22408. [PMID: 31577299 DOI: 10.1039/c9cp02996f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Our understanding of protein folds relies fundamentally on the set of secondary structures found in the proteomes. Yet, there also exist intriguing structures and motifs that are underrepresented in natural biopolymeric systems. One example is the polyproline II helix, which is usually considered to have a polar character and therefore does not form membrane spanning sections of membrane proteins. In our work, we have introduced specially designed polyproline II helices into the hydrophobic membrane milieu and used 19F NMR to monitor the helix alignment in oriented lipid bilayers. Our results show that these artificial hydrophobic peptides can adopt several different alignment states. If the helix is shorter than the thickness of the hydrophobic core of the membrane, it is submerged into the bilayer with its long axis parallel to the membrane plane. The polyproline helix adopts a transmembrane alignment when its length exceeds the bilayer thickness. If the peptide length roughly matches the lipid thickness, a coexistence of both states is observed. We thus show that the lipid thickness plays a determining role in the occurrence of a transmembrane polyproline II helix. We also found that the adaptation of polyproline II helices to hydrophobic mismatch is in some notable aspects different from α-helices. Finally, our results prove that the polyproline II helix is a competent structure for the construction of transmembrane peptide segments, despite the fact that no such motif has ever been reported in natural systems.
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Affiliation(s)
- Vladimir Kubyshkin
- Institute of Chemistry, Technical University of Berlin, Müller-Breslau-Str. 10, Berlin 10623, Germany and Department of Chemistry, University of Manitoba, Dysart Rd. 144, Winnipeg MB R3T 2N2, Canada.
| | - Stephan L Grage
- Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology (KIT), P.O.B. 3640, Karlsruhe 76021, Germany
| | - Anne S Ulrich
- Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology (KIT), P.O.B. 3640, Karlsruhe 76021, Germany and Institute of Organic Chemistry, KIT, Fritz-Haber-Weg 6, Karlsruhe 76131, Germany
| | - Nediljko Budisa
- Institute of Chemistry, Technical University of Berlin, Müller-Breslau-Str. 10, Berlin 10623, Germany and Department of Chemistry, University of Manitoba, Dysart Rd. 144, Winnipeg MB R3T 2N2, Canada.
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12
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Lipinski K, McKay MJ, Afrose F, Martfeld AN, Koeppe RE, Greathouse DV. Influence of Lipid Saturation, Hydrophobic Length and Cholesterol on Double-Arginine-Containing Helical Peptides in Bilayer Membranes. Chembiochem 2019; 20:2784-2792. [PMID: 31150136 DOI: 10.1002/cbic.201900282] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Indexed: 12/12/2022]
Abstract
Membrane proteins are essential for many cell processes yet are more difficult to investigate than soluble proteins. Charged residues often contribute significantly to membrane protein function. Model peptides such as GWALP23 (acetyl-GGALW5 LAL8 LALALAL16 ALW19 LAGA-amide) can be used to characterize the influence of specific residues on transmembrane protein domains. We have substituted R8 and R16 in GWALP23 in place of L8 and L16, equidistant from the peptide center, and incorporated specific 2 H-labeled alanine residues within the central sequence for detection by solid-state 2 H NMR spectroscopy. The resulting pattern of [2 H]Ala quadrupolar splitting (Δνq ) magnitudes indicates the core helix for R8,16 GWALP23 is significantly tilted to give a similar transmembrane orientation in thinner bilayers with either saturated C12:0 or C14:0 acyl chains (1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)) or unsaturated C16:1 Δ9 cis acyl chains. In bilayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC; C18:1 Δ9 cis) multiple orientations are indicated, whereas in longer, unsaturated 1,2-dieicosenoyl-sn-glycero-3-phosphocholine (DEiPC; C20:1 Δ11 cis) bilayers, the R8,16 GWALP23 helix adopts primarily a surface orientation. The inclusion of 10-20 mol % cholesterol in DOPC bilayers drives more of the R8,16 GWALP23 helix population to the membrane surface, thereby allowing both charged arginines access to the interfacial lipid head groups. The results suggest that hydrophobic thickness and cholesterol content are more important than lipid saturation for the arginine peptide dynamics and helix orientation in lipid membranes.
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Affiliation(s)
- Karli Lipinski
- Department of Chemistry and Biochemistry, University of Arkansas, 119 Chemistry Building, Fayetteville, AR, 72701, USA
| | - Matthew J McKay
- Department of Chemistry and Biochemistry, University of Arkansas, 119 Chemistry Building, Fayetteville, AR, 72701, USA
| | - Fahmida Afrose
- Department of Chemistry and Biochemistry, University of Arkansas, 119 Chemistry Building, Fayetteville, AR, 72701, USA
| | - Ashley N Martfeld
- Department of Chemistry and Biochemistry, University of Arkansas, 119 Chemistry Building, Fayetteville, AR, 72701, USA.,Present address: Department Department of Neurobiology, Duke University Medical Center, 311 Research Drive, Durham, NC, 27710, USA
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, 119 Chemistry Building, Fayetteville, AR, 72701, USA
| | - Denise V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas, 119 Chemistry Building, Fayetteville, AR, 72701, USA
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13
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Usery RD, Enoki TA, Wickramasinghe SP, Nguyen VP, Ackerman DG, Greathouse DV, Koeppe RE, Barrera FN, Feigenson GW. Membrane Bending Moduli of Coexisting Liquid Phases Containing Transmembrane Peptide. Biophys J 2019; 114:2152-2164. [PMID: 29742408 DOI: 10.1016/j.bpj.2018.03.026] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 03/19/2018] [Accepted: 03/22/2018] [Indexed: 11/25/2022] Open
Abstract
A number of highly curved membranes in vivo, such as epithelial cell microvilli, have the relatively high sphingolipid content associated with "raft-like" composition. Given the much lower bending energy measured for bilayers with "nonraft" low sphingomyelin and low cholesterol content, observing high curvature for presumably more rigid compositions seems counterintuitive. To understand this behavior, we measured membrane rigidity by fluctuation analysis of giant unilamellar vesicles. We found that including a transmembrane helical GWALP peptide increases the membrane bending modulus of the liquid-disordered (Ld) phase. We observed this increase at both low-cholesterol fraction and higher, more physiological cholesterol fraction. We find that simplified, commonly used Ld and liquid-ordered (Lo) phases are not representative of those that coexist. When Ld and Lo phases coexist, GWALP peptide favors the Ld phase with a partition coefficient of 3-10 depending on mixture composition. In model membranes at high cholesterol fractions, Ld phases with GWALP have greater bending moduli than the Lo phase that would coexist.
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Affiliation(s)
- Rebecca D Usery
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
| | - Thais A Enoki
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
| | - Sanjula P Wickramasinghe
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Vanessa P Nguyen
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee
| | - David G Ackerman
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Scientific Computing, Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, Virginia
| | - Denise V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
| | - Francisco N Barrera
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee
| | - Gerald W Feigenson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York.
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14
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Afrose F, McKay MJ, Mortazavi A, Suresh Kumar V, Greathouse DV, Koeppe RE. Transmembrane Helix Integrity versus Fraying To Expose Hydrogen Bonds at a Membrane-Water Interface. Biochemistry 2019; 58:633-645. [PMID: 30565458 DOI: 10.1021/acs.biochem.8b01119] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Transmembrane helices dominate the landscape for many membrane proteins. Often flanked by interfacial aromatic residues, these transmembrane helices also contain loops and interhelix segments, which could help in stabilizing a transmembrane orientation. Using 2H nuclear magnetic resonance spectroscopy to monitor bilayer-incorporated model GWALP23 family peptides, we address systematically the issue of helix fraying in relation to the dynamics and orientation of highly similar individual transmembrane helices. We inserted aromatic (Phe, Trp, Tyr, and His) or non-aromatic residues (Ala and Gly) into positions 4 and 5 adjacent to a core transmembrane helix to examine the side-chain dependency of the transmembrane orientation, dynamics, and helix integrity (extent and location of unraveling). Incorporation of [2H]alanine labels enables one to assess the helicity of the core sequence and the peptide termini. For most of the helices, we observed substantial unwinding involving at least three residues at both ends. For the unique case of histidine at positions 4 and 5, an extended N-terminal unwinding was observed up to residue 7. For further investigation of the onset of fraying, we employed A4,5GWALP23 with 2H labels at residues 4 and 5 and found that the number of terminal residues involved in the unwinding depends on bilayer thicknesses and helps to govern the helix dynamics. The combined results enable us to compare and contrast the extent of fraying for each related helix, as reflected by the deviation of experimental 2H quadrupolar splitting magnitudes of juxta-terminal alanines A3 and A21 from those represented by an ideal helix geometry.
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Affiliation(s)
- Fahmida Afrose
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Matthew J McKay
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Armin Mortazavi
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Vasupradha Suresh Kumar
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Denise V Greathouse
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
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15
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Pal S, Koeppe RE, Chattopadhyay A. Wavelength-Selective Fluorescence of a Model Transmembrane Peptide: Constrained Dynamics of Interfacial Tryptophan Anchors. J Fluoresc 2018; 28:1317-1323. [PMID: 30225736 DOI: 10.1007/s10895-018-2293-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 09/03/2018] [Indexed: 11/27/2022]
Abstract
WALPs are prototypical, α-helical transmembrane peptides that represent a consensus sequence for transmembrane segments of integral membrane proteins and serve as excellent models for exploring peptide-lipid interactions and hydrophobic mismatch in membranes. Importantly, the WALP peptides are in direct contact with the lipids. They consist of a central stretch of alternating hydrophobic alanine and leucine residues capped at both ends by tryptophans. In this work, we employ wavelength-selective fluorescence approaches to explore the intrinsic fluorescence of tryptophan residues in WALP23 in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes. Our results show that the four tryptophan residues in WALP23 exhibit an average red edge excitation shift (REES) of 6 nm, implying their localization at the membrane interface, characterized by a restricted microenvironment. This result is supported by fluorescence anisotropy and lifetime measurements as a function of wavelength displayed by WALP23 tryptophans in POPC membranes. These results provide a new approach based on intrinsic fluorescence of interfacial tryptophans to address protein-lipid interaction and hydrophobic mismatch.
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Affiliation(s)
- Sreetama Pal
- CSIR-Indian Institute of Chemical Technology, Uppal Road, Hyderabad, 500 007, India
- Academy of Scientific and Innovative Research, Ghaziabad, India
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Amitabha Chattopadhyay
- Academy of Scientific and Innovative Research, Ghaziabad, India.
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India.
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16
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McKay MJ, Martfeld AN, De Angelis AA, Opella SJ, Greathouse DV, Koeppe RE. Control of Transmembrane Helix Dynamics by Interfacial Tryptophan Residues. Biophys J 2018; 114:2617-2629. [PMID: 29874612 PMCID: PMC6129553 DOI: 10.1016/j.bpj.2018.04.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 04/06/2018] [Accepted: 04/11/2018] [Indexed: 01/12/2023] Open
Abstract
Transmembrane protein domains often contain interfacial aromatic residues, which may play a role in the insertion and stability of membrane helices. Residues such as Trp or Tyr, therefore, are often found situated at the lipid-water interface. We have examined the extent to which the precise radial locations of interfacial Trp residues may influence peptide helix orientation and dynamics. To address these questions, we have modified the GW5,19ALP23 (acetyl-GGALW5(LA)6LW19LAGA-[ethanol]amide) model peptide framework to relocate the Trp residues. Peptide orientation and dynamics were analyzed by means of solid-state nuclear magnetic resonance (NMR) spectroscopy to monitor specific 2H- and 15N-labeled residues. GW5,19ALP23 adopts a defined, tilted orientation within lipid bilayer membranes with minimal evidence of motional averaging of NMR observables, such as 2H quadrupolar or 15N-1H dipolar splittings. Here, we examine how peptide dynamics are impacted by relocating the interfacial Trp (W) residues on both ends and opposing faces of the helix, for example by a 100° rotation on the helical wheel for positions 4 and 20. In contrast to GW5,19ALP23, the modified GW4,20ALP23 helix experiences more extensive motional averaging of the NMR observables in several lipid bilayers of different thickness. Individual and combined Gaussian analyses of the 2H and 15N NMR signals confirm that the extent of dynamic averaging, particularly rotational "slippage" about the helix axis, is strongly coupled to the radial distribution of the interfacial Trp residues as well as the bilayer thickness. Additional 2H labels on alanines A3 and A21 reveal partial fraying of the helix ends. Even within the context of partial unwinding, the locations of particular Trp residues around the helix axis are prominent factors for determining transmembrane helix orientation and dynamics within the lipid membrane environment.
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Affiliation(s)
- Matthew J McKay
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
| | - Ashley N Martfeld
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
| | - Anna A De Angelis
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California
| | - Stanley J Opella
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California
| | - Denise V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas.
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17
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Vila-Viçosa D, Silva TFD, Slaybaugh G, Reshetnyak YK, Andreev OA, Machuqueiro M. Membrane-Induced p K a Shifts in wt-pHLIP and Its L16H Variant. J Chem Theory Comput 2018; 14:3289-3297. [PMID: 29733633 DOI: 10.1021/acs.jctc.8b00102] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The pH (low) insertion peptides (pHLIPs) is a family of peptides that are able to insert into a lipid bilayer at acidic pH. The molecular mechanism of pHLIPs insertion, folding, and stability in the membrane at low pH is based on multiple protonation events, which are challenging to study at the molecular level. More specifically, the relation between the experimental p K of insertion (p Kexp) of pHLIPs and the p Ka of the key residues is yet to be clarified. We carried out a computational study, complemented with new experimental data, and established the influence of (de)protonation of titrable residues on the stability of the peptide membrane-inserted state. Constant-pH molecular dynamics simulations were employed to calculate the p Ka values of these residues along the membrane normal. In the wt-pHLIP, we identified Asp14 as the key residue for the stability of the membrane-inserted state, and its p Ka value is strongly correlated with the experimental p Kexp measured in thermodynamics studies. Also, in order to narrow down the pH range at which pHLIP is stable in the membrane, we designed a new pHLIP variant, L16H, where Leu in the 16th position was replaced by a titrable His residue. Our results showed that the L16H variant undergoes two transitions. The calculated p Ka and experimentally observed p Kexp values are in good agreement. Two distinct p Kexp values delimit a pH range where the L16H peptide is stably inserted in the membrane, while, outside this range, the membrane-inserted state is destabilized and the peptide exits from the bilayer. pHLIP peptides have been successfully used to target cancer cells for the delivery of diagnostics and therapeutic agents to acidic tumors. The fine-tuning of the stability of the pHLIP inserted state and its restriction to a narrow well-defined pH range might allow the design of new peptides, able to discriminate between tissues with different extracellular pH values.
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Affiliation(s)
- Diogo Vila-Viçosa
- Centro de Química e Bioquímica, BioISI: Biosystems and Integrative Sciences Institute, Departamento de Química e Bioquímica, Faculdade de Ciências , Universidade de Lisboa , 1749-016 Lisboa , Portugal
| | - Tomás F D Silva
- Centro de Química e Bioquímica, BioISI: Biosystems and Integrative Sciences Institute, Departamento de Química e Bioquímica, Faculdade de Ciências , Universidade de Lisboa , 1749-016 Lisboa , Portugal
| | - Gregory Slaybaugh
- Department of Physics , University of Rhode Island , 2 Lippitt Road , Kingston , Rhode Island 02881 , United States
| | - Yana K Reshetnyak
- Department of Physics , University of Rhode Island , 2 Lippitt Road , Kingston , Rhode Island 02881 , United States
| | - Oleg A Andreev
- Department of Physics , University of Rhode Island , 2 Lippitt Road , Kingston , Rhode Island 02881 , United States
| | - Miguel Machuqueiro
- Centro de Química e Bioquímica, BioISI: Biosystems and Integrative Sciences Institute, Departamento de Química e Bioquímica, Faculdade de Ciências , Universidade de Lisboa , 1749-016 Lisboa , Portugal
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18
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Kozic M, Fox SJ, Thomas JM, Verma CS, Rigden DJ. Large scale ab initio modeling of structurally uncharacterized antimicrobial peptides reveals known and novel folds. Proteins 2018; 86:548-565. [DOI: 10.1002/prot.25473] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 01/16/2018] [Accepted: 01/29/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Mara Kozic
- Institute of Integrative Biology, University of Liverpool; Liverpool L69 7ZB U.K
- Agency for Science, Technology and Research (A*STAR), Bioinformatics Institute; Singapore
| | - Stephen J. Fox
- Agency for Science, Technology and Research (A*STAR), Bioinformatics Institute; Singapore
| | - Jens M. Thomas
- Institute of Integrative Biology, University of Liverpool; Liverpool L69 7ZB U.K
| | - Chandra S. Verma
- Agency for Science, Technology and Research (A*STAR), Bioinformatics Institute; Singapore
- Department of Biological Sciences; National University of Singapore; Singapore
- School of Biological Sciences; Nanyang Technological University; Singapore
| | - Daniel J. Rigden
- Institute of Integrative Biology, University of Liverpool; Liverpool L69 7ZB U.K
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19
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McKay MJ, Afrose F, Koeppe RE, Greathouse DV. Helix formation and stability in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2108-2117. [PMID: 29447916 DOI: 10.1016/j.bbamem.2018.02.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 02/06/2018] [Accepted: 02/07/2018] [Indexed: 01/05/2023]
Abstract
In this article we review current understanding of basic principles for the folding of membrane proteins, focusing on the more abundant alpha-helical class. Membrane proteins, vital to many biological functions and implicated in numerous diseases, fold into their active conformations in the complex environment of the cell bilayer membrane. While many membrane proteins rely on the translocon and chaperone proteins to fold correctly, others can achieve their functional form in the absence of any translation apparatus or other aides. Nevertheless, the spontaneous folding process is not well understood at the molecular level. Recent findings suggest that helix fraying and loop formation may be important for overall structure, dynamics and regulation of function. Several types of membrane helices with ionizable amino acids change their topology with pH. Additionally we note that some peptides, including many that are rich in arginine, and a particular analogue of gramicidin, are able passively to translocate across cell membranes. The findings indicate that a final protein structure in a lipid-bilayer membrane is sequence-based, with lipids contributing to stability and regulation. While much progress has been made toward understanding the folding process for alpha-helical membrane proteins, it remains a work in progress. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.
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Affiliation(s)
- Matthew J McKay
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Fahmida Afrose
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
| | - Denise V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA.
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20
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Sandoval A, Eichler S, Madathil S, Reeves PJ, Fahmy K, Böckmann RA. The Molecular Switching Mechanism at the Conserved D(E)RY Motif in Class-A GPCRs. Biophys J 2017; 111:79-89. [PMID: 27410736 DOI: 10.1016/j.bpj.2016.06.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 05/31/2016] [Accepted: 06/08/2016] [Indexed: 10/21/2022] Open
Abstract
The disruption of ionic and H-bond interactions between the cytosolic ends of transmembrane helices TM3 and TM6 of class-A (rhodopsin-like) G protein-coupled receptors (GPCRs) is a hallmark for their activation by chemical or physical stimuli. In the bovine photoreceptor rhodopsin, this is accompanied by proton uptake at Glu(134) in the class-conserved D(E)RY motif. Studies on TM3 model peptides proposed a crucial role of the lipid bilayer in linking protonation to stabilization of an active state-like conformation. However, the molecular details of this linkage could not be resolved and have been addressed in this study by molecular dynamics (MD) simulations on TM3 model peptides in a bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We show that protonation of the conserved glutamic acid alters the peptide insertion depth in the membrane, its side-chain rotamer preferences, and stabilizes the C-terminal helical structure. These factors contribute to the rise of the side-chain pKa (> 6) and to reduced polarity around the TM3 C terminus as confirmed by fluorescence spectroscopy. Helix stabilization requires the protonated carboxyl group; unexpectedly, this stabilization could not be evoked with an amide in MD simulations. Additionally, time-resolved Fourier transform infrared (FTIR) spectroscopy of TM3 model peptides revealed a different kinetics for lipid ester carbonyl hydration, suggesting that the carboxyl is linked to more extended H-bond clusters than an amide. Remarkably, this was seen as well in DOPC-reconstituted Glu(134)- and Gln(134)-containing bovine opsin mutants and demonstrates that the D(E)RY motif is a hydrated microdomain. The function of the D(E)RY motif as a proton switch is suggested to be based on the reorganization of the H-bond network at the membrane interface.
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Affiliation(s)
- Angelica Sandoval
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Stefanie Eichler
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Resource Ecology, and Technische Universität Dresden, Dresden, Germany
| | - Sineej Madathil
- Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Philip J Reeves
- School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - Karim Fahmy
- Helmholtz-Zentrum Dresden - Rossendorf, Institute of Resource Ecology, and Technische Universität Dresden, Dresden, Germany.
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
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21
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Usery RD, Enoki TA, Wickramasinghe SP, Weiner MD, Tsai WC, Kim MB, Wang S, Torng TL, Ackerman DG, Heberle FA, Katsaras J, Feigenson GW. Line Tension Controls Liquid-Disordered + Liquid-Ordered Domain Size Transition in Lipid Bilayers. Biophys J 2017; 112:1431-1443. [PMID: 28402885 DOI: 10.1016/j.bpj.2017.02.033] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/27/2017] [Accepted: 02/16/2017] [Indexed: 12/28/2022] Open
Abstract
To better understand animal cell plasma membranes, we studied simplified models, namely four-component lipid bilayer mixtures. Here we describe the domain size transition in the region of coexisting liquid-disordered (Ld) + liquid-ordered (Lo) phases. This transition occurs abruptly in composition space with domains increasing in size by two orders of magnitude, from tens of nanometers to microns. We measured the line tension between coexisting Ld and Lo domains close to the domain size transition for a variety of lipid mixtures, finding that in every case the transition occurs at a line tension of ∼0.3 pN. A computational model incorporating line tension and dipole repulsion indicated that even small changes in line tension can result in domains growing in size by several orders of magnitude, consistent with experimental observations. We find that other properties of the coexisting Ld and Lo phases do not change significantly in the vicinity of the abrupt domain size transition.
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Affiliation(s)
- Rebecca D Usery
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
| | - Thais A Enoki
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
| | - Sanjula P Wickramasinghe
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Department of Biochemistry and Biophysics at the University of Pennsylvania, Philadelphia, Pennsylvania
| | | | - Wen-Chyan Tsai
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
| | - Mary B Kim
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Shu Wang
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Harvard Medical School Library of Integrated Network-based Cellular Signatures Center and Laboratory of Systems Pharmacology, Harvard University, Boston, Massachusetts
| | - Thomas L Torng
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Department of Biochemistry, Geisel School of Medicine at Dartmouth College, Hanover, New Hampshire
| | - David G Ackerman
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York; Scientific Computing, Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, Virginia
| | - Frederick A Heberle
- Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; The Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, Tennessee
| | - John Katsaras
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee
| | - Gerald W Feigenson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York.
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22
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23
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Towle KM, Vederas JC. Structural features of many circular and leaderless bacteriocins are similar to those in saposins and saposin-like peptides. MEDCHEMCOMM 2017; 8:276-285. [PMID: 30108744 PMCID: PMC6072434 DOI: 10.1039/c6md00607h] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 12/09/2016] [Indexed: 12/14/2022]
Abstract
Bacteriocins are potent antimicrobial peptides that are ribosomally produced and exported by bacteria, presumably to aid elimination of competing microorganisms. Many circular and linear leaderless bacteriocins have a recuring three dimensional structural motif known as a saposin-like fold. Although these bacteriocin sizes and sequences are often quite different, and their mechanisms of action vary, this conserved motif of multiple helices appears critical for activity and may enable peptide-lipid and peptide-receptor interactions in target bacterial cell membranes. Comparisons between electrostatic surfaces and hydrophobic surface maps of different bacteriocins are discussed emphasizing similarities and differences in the context of proposed modes of action.
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Affiliation(s)
- K M Towle
- Department of Chemistry , University of Alberta , Edmonton , Alberta , T6G 2G2 Canada .
| | - J C Vederas
- Department of Chemistry , University of Alberta , Edmonton , Alberta , T6G 2G2 Canada .
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24
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Rajagopalan V, Greathouse DV, Koeppe RE. Influence of glutamic acid residues and pH on the properties of transmembrane helices. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:484-492. [PMID: 28069412 DOI: 10.1016/j.bbamem.2017.01.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 12/13/2016] [Accepted: 01/04/2017] [Indexed: 11/13/2022]
Abstract
Negatively charged side chains are important for the function of particular ion channels and certain other membrane proteins. To investigate the influence of single glutamic acid side chains on helices that span lipid-bilayer membranes, we have employed GWALP23 (acetyl-GGALW5LALALALALALALW19LAGA-amide) as a favorable host peptide framework. We substituted individual Leu residues with Glu residues (L12E or L14E or L16E) and incorporated specific 2H-labeled alanine residues within the core helical region or near the ends of the sequence. Solid-state 2H NMR spectra reveal little change for the core labels in GWALP23-E12, -E14 and -E16 over a pH range of 4 to 12.5, with the spectra being broader for samples in DOPC compared to DLPC bilayers. The spectra for samples with deuterium labels near the helix ends on alanines 3 and 21 show modest pH-dependent changes in the extent of unwinding of the helix terminals in DLPC and DOPC bilayers. The combined results indicate minor overall responses of these transmembrane helices to changes in pH, with the most buried residue E12 showing no pH dependence. While the Glu residues E14 and E16 may have high pKa values in the lipid bilayer environment, it is also possible that a paucity of helix response is masking the pKa values. Interestingly, when E16 is present, spectral changes at high pH report significant local unwinding of the core helix. Our results are consistent with the expectation that buried carboxyl groups aggressively hold their protons and/or waters of hydration.
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Affiliation(s)
- Venkatesan Rajagopalan
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, United States
| | - Denise V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, United States
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, United States.
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25
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Thibado JK, Martfeld AN, Greathouse DV, Koeppe RE. Influence of High pH and Cholesterol on Single Arginine-Containing Transmembrane Peptide Helices. Biochemistry 2016; 55:6337-6343. [PMID: 27782382 PMCID: PMC5266483 DOI: 10.1021/acs.biochem.6b00896] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
![]()
An essential component
of mammalian cells, cholesterol exerts significant
influence on the physical properties of the cell membrane and in turn
its constituents, including membrane proteins. Although sparse, polar
amino acid residues are highly conserved in membrane proteins and
play pivotal roles in determining specific structural and functional
properties. To improve our understanding of particular polar residues
in the membrane environment, we have examined two specific “guest”
Arg residues within a well-defined and deuterium-labeled “host”
framework provided by the transmembrane helical peptide GWALP23 (acetyl-GGALWLALALALALALALWLAGA-amide).
Solid-state 2H nuclear magnetic resonance (NMR) spectra
from aligned bilayer membrane samples effectively report changes in
the host helix properties because of the incorporation of the guest
residues. The focus of this work is two-pronged. First, GWALP23-R14
was examined over a pH range of 2–13 in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) ester- or ether-linked
bilayer membranes. Our findings indicate that the Arg guanidinium
side chain remains charged over this entire range, in agreement with
numerous molecular dynamics simulations. Second, GWALP23-R12 and GWALP23-R14
peptides were characterized in DOPC bilayers with varying cholesterol
content. Our findings suggest that 10 or 20% cholesterol content has
minimal impact on the orientation of the R14 peptide. Although the
NMR signals are broader and weaker in the presence of 20% cholesterol,
the deuterium quadrupolar splittings for [2H]Ala residues
in GWALP23-R14 change very little. Conversely, cholesterol appears
to modulate the multistate behavior of GWALP23-R12 and to favor a
major interfacial state for the helix, bound at the bilayer surface.
These results indicate a conditional sensitivity of a complex multistate
transmembrane Arg-containing peptide helix to the presence of cholesterol.
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Affiliation(s)
- Jordana K Thibado
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
| | - Ashley N Martfeld
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
| | - Denise V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
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26
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Mortazavi A, Rajagopalan V, Sparks KA, Greathouse DV, Koeppe RE. Juxta-terminal Helix Unwinding as a Stabilizing Factor to Modulate the Dynamics of Transmembrane Helices. Chembiochem 2016; 17:462-5. [PMID: 26749271 PMCID: PMC4820057 DOI: 10.1002/cbic.201500656] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Indexed: 12/24/2022]
Abstract
Transmembrane helices of integral membrane proteins often are flanked by interfacial aromatic residues that can serve as anchors to aid the stabilization of a tilted transmembrane orientation. Yet, physical factors that govern the orientation or dynamic averaging of individual transmembrane helices are not well understood and have not been adequately explained. Using solid-state (2) H NMR spectroscopy to examine lipid bilayer-incorporated model peptides of the GWALP23 (acetyl-GGALW(LA)6 LWLAGA-amide) family, we observed substantial unwinding at the terminals of several tilted helices spanning the membranes of DLPC, DMPC, or DOPC lipid bilayers. The fraying of helix ends might be vital for defining the dynamics and orientations of transmembrane helices in lipid bilayer membranes.
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Affiliation(s)
- Armin Mortazavi
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, 72701, USA
| | - Venkatesan Rajagopalan
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, 72701, USA
| | - Kelsey A Sparks
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, 72701, USA
| | - Denise V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, 72701, USA
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, 72701, USA.
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27
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Johnson MA, Ray BD, Wassall SR, Petrache HI. Equivalent Isopropanol Concentrations of Aromatic Amino Acids Interactions with Lipid Vesicles. J Membr Biol 2015; 248:695-703. [PMID: 25691267 DOI: 10.1007/s00232-015-9781-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 01/30/2015] [Indexed: 11/26/2022]
Abstract
We show that the interaction of aromatic amino acids with lipid bilayers can be characterized by conventional 1D [Formula: see text]H NMR spectroscopy using reference spectra obtained in isopropanol-d8/D[Formula: see text]O solutions. We demonstrate the utility of this method with three different peptides containing tyrosine, tryptophan, or phenylalanine amino acids in the presence of 1,2-dioleoyl-sn-glycero-3-phosphocholine or 1,2-dioleoyl-sn-glycero-3-phosphoserine lipid membranes. In each case, we determine an equivalent isopropanol concentration (EIC) for each hydrogen site of aromatic groups, in essence constructing a map of the chemical environment. These EIC maps provide information on relative affinities of aromatic side chains for either PC or PS bilayers and also inform on amino acid orientation preference when bound to membranes.
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Affiliation(s)
- Merrell A Johnson
- Department of Physics, Indiana University Purdue University Indianapolis, 402 N Blackford St., Indianapolis, IN, 46202, USA,
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28
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Dynamic regulation of lipid-protein interactions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1849-59. [PMID: 25666872 DOI: 10.1016/j.bbamem.2015.01.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 01/27/2015] [Accepted: 01/29/2015] [Indexed: 02/07/2023]
Abstract
We review the importance of helix motions for the function of several important categories of membrane proteins and for the properties of several model molecular systems. For voltage-gated potassium or sodium channels, sliding, tilting and/or rotational movements of the S4 helix accompanied by a swapping of cognate side-chain ion-pair interactions regulate the channel gating. In the seven-helix G protein-coupled receptors, exemplified by the rhodopsins, collective helix motions serve to activate the functional signaling. Peptides which initially associate with lipid-bilayer membrane surfaces may undergo dynamic transitions from surface-bound to tilted-transmembrane orientations, sometimes accompanied by changes in the molecularity, formation of a pore or, more generally, the activation of biological function. For single-span membrane proteins, such as the tyrosine kinases, an interplay between juxtamembrane and transmembrane domains is likely to be crucial for the regulation of dimer assembly that in turn is associated with the functional responses to external signals. Additionally, we note that experiments with designed single-span transmembrane helices offer fundamental insights into the molecular features that govern protein-lipid interactions. This article is part of a Special Issue entitled: Lipid-protein interactions.
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29
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Botelho SC, Enquist K, von Heijne G, Draheim RR. Differential repositioning of the second transmembrane helices from E. coli Tar and EnvZ upon moving the flanking aromatic residues. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:615-21. [PMID: 25445668 DOI: 10.1016/j.bbamem.2014.11.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 10/29/2014] [Accepted: 11/17/2014] [Indexed: 01/04/2023]
Abstract
Aromatic tuning, i.e. repositioning aromatic residues found at the cytoplasmic end of transmembrane (TM) domains within bacterial receptors, has been previously shown to modulate signal output from the aspartate chemoreceptor (Tar) and the major osmosensor EnvZ of Escherichia coli. In the case of Tar, changes in signal output consistent with the vertical position of the native Trp-Tyr aromatic tandem within TM2 were observed. In contrast, within EnvZ, where a Trp-Leu-Phe aromatic triplet was repositioned, the surface that the triplet resided upon was the major determinant governing signal output. However, these studies failed to determine whether moving the aromatic residues was sufficient to physically reposition the TM helix within a membrane. Recent coarse-grained molecular dynamics (CG-MD) simulations predicted displacement of Tar TM2 upon moving the aromatic residues at the cytoplasmic end of the helix. Here, we demonstrate that repositioning the Trp-Tyr tandem within Tar TM2 displaces the C-terminal boundary of the helix relative to the membrane. In a similar analysis of EnvZ, an abrupt initial displacement of TM2 was observed but no subsequent movement was seen, suggesting that the vertical position of TM2 is not governed by the location of the Trp-Leu-Phe triplet. Our results also provide another set of experimental data, i.e. the resistance of EnvZ TM2 to being displaced upon aromatic tuning, which could be useful for subsequent refinement of the initial CG-MD simulations. Finally, we discuss the limitations of these methodologies, how moving flanking aromatic residues might impact steady-state signal output and the potential to employ aromatic tuning in other bacterial membrane-spanning receptors.
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Affiliation(s)
- Salomé C Botelho
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Karl Enquist
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Gunnar von Heijne
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
| | - Roger R Draheim
- Division of Pharmacy, Durham University, Queen's Campus, Stockton-on-Tees TS17 6BH, England, UK; Wolfson Research Institute for Health and Wellbeing, Durham University, Queen's Campus, Stockton-on-Tees, TS17 6BH, England, UK.
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30
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Sparks KA, Gleason NJ, Gist R, Langston R, Greathouse DV, Koeppe RE. Comparisons of interfacial Phe, Tyr, and Trp residues as determinants of orientation and dynamics for GWALP transmembrane peptides. Biochemistry 2014; 53:3637-45. [PMID: 24829070 PMCID: PMC4053069 DOI: 10.1021/bi500439x] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
![]()
Aromatic
amino acids often flank the transmembrane alpha helices
of integral membrane proteins. By favoring locations within the membrane–water
interface of the lipid bilayer, aromatic residues Trp, Tyr, and sometimes
Phe may serve as anchors to help stabilize a transmembrane orientation.
In this work, we compare the influence of interfacial Trp, Tyr, or
Phe residues upon the properties of tilted helical transmembrane peptides.
For such comparisons, it has been critical to start with no more than
one interfacial aromatic residue near each end of a transmembrane
helix, for example, that of GWALP23 (acetyl-GGALW5(LA)6LW19LAGA-[ethanol]amide). To this end, we have
employed 2H-labeled alanines and solid-state NMR spectroscopy
to investigate the consequences of moving or replacing W5 or W19 in
GWALP23 with selected Tyr, Phe, or Trp residues at the same or proximate
locations. We find that GWALP23 peptides having F5, Y5, or W5 exhibit
essentially the same average tilt and similar dynamics in bilayer
membranes of 1,2-dilauroylphosphatidylcholine (DLPC) or 1,2-dioleoylphosphatidylcholine
(DOPC). When double Tyr anchors are present, in Y4,5GWALP23
the NMR observables are markedly more subject to dynamic averaging
and at the same time are less responsive to the bilayer thickness.
Decreased dynamics are nevertheless observed when ring hydrogen bonding
is removed, such that F4,5GWALP23 exhibits a similar extent
of low dynamic averaging as GWALP23 itself. When F5 is the sole aromatic
group in the N-interfacial region, the dynamic averaging is (only)
slightly more extensive than with W5, Y5, or Y4 alone or with F4,5,
yet it is much less than that observed for Y4,5GWALP23.
Interestingly, moving Y5 to Y4 or W19 to W18, while retaining only
one hydrogen-bond-capable aromatic ring at each interface, maintains
the low level of dynamic averaging but alters the helix azimuthal
rotation. The rotation change is about 40° for Y4 regardless
of whether the host lipid bilayer is DLPC or DOPC. The rotational
change (Δρ) is more dramatic and more complex when W19
is moved to W18, as Δρ is about +90° in DLPC but
about −60° in DOPC. Possible reasons for this curious
lipid-dependent helix rotation could include not only the separation
distances between flanking aromatic or hydrophobic residues but also
the absolute location of the W19 indole ring. For the more usual cases,
when the helix azimuthal rotation shows little dependence on the host
bilayer identity, excepting W18GWALP23, the transmembrane
helices adapt to different lipids primarily by changing the magnitude
of their tilt. We conclude that, in the absence of other functional
groups, interfacial aromatic residues determine the preferred orientations
and dynamics of membrane-spanning peptides. The results furthermore
suggest possibilities for rotational and dynamic control of membrane
protein function.
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Affiliation(s)
- Kelsey A Sparks
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
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31
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Differential regulation of staphylococcal virulence by the sensor kinase SaeS in response to neutrophil-derived stimuli. Proc Natl Acad Sci U S A 2014; 111:E2037-45. [PMID: 24782537 DOI: 10.1073/pnas.1322125111] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Two-component systems (TCSs) are highly conserved across bacteria and are used to rapidly sense and respond to changing environmental conditions. The human pathogen Staphylococcus aureus uses the S. aureus exoprotein expression (sae) TCS to sense host signals and activate transcription of virulence factors essential to pathogenesis. Despite its importance, the mechanism by which the histidine kinase SaeS recognizes specific host stimuli is unknown. After mutagenizing the predicted extracellular loop of SaeS, we discovered one methionine residue (M31) was essential for the ability of S. aureus to transcribe sae target genes, including hla, lukAB/lukGH, and hlgA. This single M31A mutation also significantly reduced cytotoxicity in human neutrophils to levels observed in cells following interaction with ΔsaeS. Another important discovery was that mutation of two aromatic anchor residues (W32A and F33A) disrupted the normal basal signaling of SaeS in the absence of inducing signals, yet both mutant kinases had appropriate activation of effector genes following exposure to neutrophils. Although the transcriptional profile of aromatic mutation W32A was consistent with that of WT in response to human α-defensin 1, mutant kinase F33A did not properly transcribe the γ-toxin genes in response to this stimulus. Taken together, our results provide molecular evidence for how SaeS recognizes host signals and triggers activation of select virulence factors to facilitate evasion of innate immunity. These findings have important implications for signal transduction in prokaryotes and eukaryotes due to conservation of aromatic anchor residues across both of these domains and the important role they play in sensor protein structure and function.
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32
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Wadhwani P, Strandberg E, van den Berg J, Mink C, Bürck J, Ciriello RA, Ulrich AS. Dynamical structure of the short multifunctional peptide BP100 in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:940-9. [DOI: 10.1016/j.bbamem.2013.11.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 10/25/2013] [Accepted: 11/01/2013] [Indexed: 11/26/2022]
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33
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Gleason NJ, Greathouse DV, Grant CV, Opella SJ, Koeppe RE. Single tryptophan and tyrosine comparisons in the N-terminal and C-terminal interface regions of transmembrane GWALP peptides. J Phys Chem B 2013; 117:13786-94. [PMID: 24111589 DOI: 10.1021/jp407542e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Hydrophobic membrane-spanning helices often are flanked by interfacial aromatic or charged residues. In this paper, we compare the consequences of single Trp → Tyr substitutions at each interface for the properties of a defined transmembrane helix in the absence of charged residues. The choice of molecular framework is critical for these single-residue experiments because the presence of "too many" aromatic residues (more than one at either membrane-water interface) introduces excess dynamic averaging of solid state NMR observables. To this end, we compare the outcomes when changing W(5) or W(19), or both of them, to tyrosine in the well-characterized transmembrane peptide acetyl-GGALW(5)(LA)6LW(19)LAGA-amide ("GWALP23"). By means of solid-state (2)H and (15)N NMR experiments, we find that Y(19)GW(5)ALP23 displays similar magnitudes of peptide helix tilt as Y(5)GW(19)ALP23 and responds similarly to changes in bilayer thickness, from DLPC to DMPC to DOPC. The presence of Y(19) changes the azimuthal rotation angle ρ (about the helix axis) to a similar extent as Y(5), but in the opposite direction. When tyrosines are substituted for both tryptophans to yield GY(5,19)ALP23, the helix tilt angle is again of comparable magnitude, and furthermore, the preferred azimuthal rotation angle ρ is relatively unchanged from that of GW(5,19)ALP23. The extent of dynamic averaging increases marginally when Tyr replaces Trp. Yet, importantly, all members of the peptide family having single Tyr or Trp residues near each interface exhibit only moderate and not highly extensive dynamic averaging. The results provide important benchmarks for evaluating conformational and dynamic control of membrane protein function.
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Affiliation(s)
- Nicholas J Gleason
- Department of Chemistry and Biochemistry, University of Arkansas , Fayetteville, Arkansas 72701, United States
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34
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Sánchez-Muñoz OL, Strandberg E, Esteban-Martín E, Grage SL, Ulrich AS, Salgado J. Canonical azimuthal rotations and flanking residues constrain the orientation of transmembrane helices. Biophys J 2013; 104:1508-16. [PMID: 23561527 DOI: 10.1016/j.bpj.2013.02.030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 01/31/2013] [Accepted: 02/20/2013] [Indexed: 12/22/2022] Open
Abstract
In biological membranes the alignment of embedded proteins provides crucial structural information. The transmembrane (TM) parts have well-defined secondary structures, in most cases α-helices and their orientation is given by a tilt angle and an azimuthal rotation angle around the main axis. The tilt angle is readily visualized and has been found to be functionally relevant. However, there exist no general concepts on the corresponding azimuthal rotation. Here, we show that TM helices prefer discrete rotation angles. They arise from a combination of intrinsic properties of the helix geometry plus the influence of the position and type of flanking residues at both ends of the hydrophobic core. The helical geometry gives rise to canonical azimuthal angles for which the side chains of residues from the two ends of the TM helix tend to have maximum or minimum immersion within the membrane. This affects the preferential position of residues that fall near hydrophobic/polar interfaces of the membrane, depending on their hydrophobicity and capacity to form specific anchoring interactions. On this basis, we can explain the orientation and dynamics of TM helices and make accurate predictions, which correspond well to the experimental values of several model peptides (including dimers), and TM segments of polytopic membrane proteins.
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35
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A distinct mechanism for activating uncoupled nicotinic acetylcholine receptors. Nat Chem Biol 2013; 9:701-7. [DOI: 10.1038/nchembio.1338] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 08/06/2013] [Indexed: 01/08/2023]
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36
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Hong H, Rinehart D, Tamm LK. Membrane depth-dependent energetic contribution of the tryptophan side chain to the stability of integral membrane proteins. Biochemistry 2013; 52:4413-21. [PMID: 23763479 DOI: 10.1021/bi400344b] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Lipid solvation provides the primary driving force for the insertion and folding of integral membrane proteins. Although the structure of the lipid bilayer is often simplified as a central hydrophobic core sandwiched between two hydrophilic interfacial regions, the complexity of the liquid-crystalline bilayer structure and the gradient of water molecules across the bilayer fine-tune the energetic contributions of individual amino acid residues to the stability of membrane proteins at different depths of the bilayer. The tryptophan side chain is particularly interesting because despite its widely recognized role in anchoring membrane proteins in lipid bilayers, there is little consensus about its hydrophobicity among various experimentally determined hydrophobicity scales. Here we investigated how lipid-facing tryptophan residues located at different depths in the bilayer contribute to the stability of integral membrane proteins using outer membrane protein A (OmpA) as a model. We replaced all lipid-contacting residues of the first transmembrane β-strand of OmpA with alanines and individually incorporated tryptophans in these positions along the strand. By measuring the thermodynamic stability of these proteins, we found that OmpA is slightly more stable when tryptophans are placed in the center of the bilayer and that it is somewhat destabilized as tryptophans approach the interfacial region. However, this trend may be partially reversed when a moderate concentration of urea rather than water is taken as the reference state. The measured stability profiles are driven by similar profiles of the m-value, a parameter that reflects the shielding of hydrophobic surface area from water. Our results indicate that knowledge of the free energy level of the protein's unfolded reference state is important for quantitatively assessing the stability of membrane proteins, which may explain differences in observed profiles between in vivo and in vitro scales.
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Affiliation(s)
- Heedeok Hong
- Department of Chemistry and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States.
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37
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Buried lysine, but not arginine, titrates and alters transmembrane helix tilt. Proc Natl Acad Sci U S A 2013; 110:1692-5. [PMID: 23319623 DOI: 10.1073/pnas.1215400110] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The ionization states of individual amino acid residues of membrane proteins are difficult to decipher or assign directly in the lipid-bilayer membrane environment. We address this issue for lysines and arginines in designed transmembrane helices. For lysines (but not arginines) at two locations within dioleoyl-phosphatidylcholine bilayer membranes, we measure pK(a) values below 7.0. We find that buried charged lysine, in fashion similar to arginine, will modulate helix orientation to maximize its own access to the aqueous interface or, if occluded by aromatic rings, may cause a transmembrane helix to exit the lipid bilayer. Interestingly, the influence of neutral lysine (vis-à-vis leucine) upon helix orientation also depends upon its aqueous access. Our results suggest that changes in the ionization states of particular residues will regulate membrane protein function and furthermore illustrate the subtle complexity of ionization behavior with respect to the detailed lipid and protein environment.
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38
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Rankenberg JM, Vostrikov VV, Greathouse DV, Grant CV, Opella SJ, Koeppe RE. Properties of membrane-incorporated WALP peptides that are anchored on only one end. Biochemistry 2012; 51:10066-74. [PMID: 23171005 DOI: 10.1021/bi301394z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Peptides of the "WALP" family, acetyl-GWW(LA)(n)LWWA-[ethanol]amide, have proven to be opportune models for investigating lipid-peptide interactions. Because the average orientations and motional behavior of the N- and C-terminal Trp (W) residues differ, it is of interest to investigate how the positions of the tryptophans influence the properties of the membrane-incorporated peptides. To address this question, we synthesized acetyl-GGWW(LA)(n)-ethanolamide and acetyl-(AL)(n)WWG-ethanolamide, in which n = 4 or 8, which we designate as "N-anchored" and "C-anchored" peptides, respectively. Selected (2)H or (15)N labels were incorporated for solid-state nuclear magnetic resonance (NMR) spectroscopy. These peptides can be considered "half"-anchored WALP peptides, having only one pair of interfacial Trp residues near either the amino or the carboxyl terminus. The hydrophobic lengths of the (n = 8) peptides are similar to that of WALP23. These longer half-anchored WALP peptides incorporate into lipid bilayers as α-helices, as reflected in their circular dichroism spectra. Solid-state NMR experiments indicate that the longer peptide helices assume defined transmembrane orientations with small non-zero average tilt angles and moderate to high dynamic averaging in bilayer membranes of 1,2-dioleoylphosphatidylcholine, 1,2-dimyristoylphosphatidylcholine, and 1,2-dilauroylphosphatidylcholine. The intrinsically small apparent tilt angles suggest that interactions of aromatic residues with lipid headgroups may play an important role in determining the magnitude of the peptide tilt in the bilayer membrane. The shorter (n = 4) peptides, in stark contrast to the longer peptides, display NMR spectra that are characteristic of greatly reduced motional averaging, probably because of peptide aggregation in the bilayer environment, and CD spectra that are characteristic of β-structure.
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Affiliation(s)
- Johanna M Rankenberg
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, USA
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39
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Rankenberg JM, Vostrikov VV, DuVall CD, Greathouse DV, Koeppe RE, Grant CV, Opella SJ. Proline kink angle distributions for GWALP23 in lipid bilayers of different thicknesses. Biochemistry 2012; 51:3554-64. [PMID: 22489564 DOI: 10.1021/bi300281k] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
By using selected (2)H and (15)N labels, we have examined the influence of a central proline residue on the properties of a defined peptide that spans lipid bilayer membranes by solid-state nuclear magnetic resonance (NMR) spectroscopy. For this purpose, GWALP23 (acetyl-GGALW(5)LALALALALALALW(19)LAGA-ethanolamide) is a suitable model peptide that employs, for the purpose of interfacial anchoring, only one tryptophan residue on either end of a central α-helical core sequence. Because of its systematic behavior in lipid bilayer membranes of differing thicknesses [Vostrikov, V. V., et al. (2010) J. Biol. Chem. 285, 31723-31730], we utilize GWALP23 as a well-characterized framework for introducing guest residues within a transmembrane sequence; for example, a central proline yields acetyl-GGALW(5)LALALAP(12)ALALALW(19)LAGA-ethanolamide. We synthesized GWALP23-P12 with specifically placed (2)H and (15)N labels for solid-state NMR spectroscopy and examined the peptide orientation and segmental tilt in oriented DMPC lipid bilayer membranes using combined (2)H GALA and (15)N-(1)H high-resolution separated local field methods. In DMPC bilayer membranes, the peptide segments N-terminal and C-terminal to the proline are both tilted substantially with respect to the bilayer normal, by ~34 ± 5° and 29 ± 5°, respectively. While the tilt increases for both segments when proline is present, the range and extent of the individual segment motions are comparable to or smaller than those of the entire GWALP23 peptide in bilayer membranes. In DMPC, the proline induces a kink of ~30 ± 5°, with an apparent helix unwinding or "swivel" angle of ~70°. In DLPC and DOPC, on the basis of (2)H NMR data only, the kink angle and swivel angle probability distributions overlap those of DMPC, yet the most probable kink angle appears to be somewhat smaller than in DMPC. As has been described for GWALP23 itself, the C-terminal helix ends before Ala(21) in the phospholipids DMPC and DLPC yet remains intact through Ala(21) in DOPC. The dynamics of bilayer-incorporated, membrane-spanning GWALP23 and GWALP23-P12 are less extensive than those observed for WALP family peptides that have more than two interfacial Trp residues.
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Affiliation(s)
- Johanna M Rankenberg
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
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