1
|
Li Y, Yang KD, Kong DC, Ye JF. Advances in phage display based nano immunosensors for cholera toxin. Front Immunol 2023; 14:1224397. [PMID: 37781379 PMCID: PMC10534012 DOI: 10.3389/fimmu.2023.1224397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 08/23/2023] [Indexed: 10/03/2023] Open
Abstract
Cholera, a persistent global public health concern, continues to cause outbreaks in approximately 30 countries and territories this year. The imperative to safeguard water sources and food from Vibrio cholerae, the causative pathogen, remains urgent. The bacterium is mainly disseminated via ingestion of contaminated water or food. Despite the plate method's gold standard status for detection, its time-consuming nature, taking several days to provide results, remains a challenge. The emergence of novel virulence serotypes raises public health concerns, potentially compromising existing detection methods. Hence, exploiting Vibrio cholerae toxin testing holds promise due to its inherent stability. Immunobiosensors, leveraging antibody specificity and sensitivity, present formidable tools for detecting diverse small molecules, encompassing drugs, hormones, toxins, and environmental pollutants. This review explores cholera toxin detection, highlighting phage display-based nano immunosensors' potential. Engineered bacteriophages exhibit exceptional cholera toxin affinity, through specific antibody fragments or mimotopes, enabling precise quantification. This innovative approach promises to reshape cholera toxin detection, offering an alternative to animal-derived methods. Harnessing engineered bacteriophages aligns with ethical detection and emphasizes sensitivity and accuracy, a pivotal stride in the evolution of detection strategies. This review primarily introduces recent advancements in phage display-based nano immunosensors for cholera toxin, encompassing technical aspects, current challenges, and future prospects.
Collapse
Affiliation(s)
- Yang Li
- General Surgery Center, First Hospital of Jilin University, Changchun, Jilin, China
- School of Nursing, Jilin University, Changchun, China
| | - Kai-di Yang
- School of Nursing, Jilin University, Changchun, China
| | - De-cai Kong
- General Surgery Center, First Hospital of Jilin University, Changchun, Jilin, China
| | - Jun-feng Ye
- General Surgery Center, First Hospital of Jilin University, Changchun, Jilin, China
| |
Collapse
|
2
|
Haase M, Tessmer L, Köhnlechner L, Kuhn A. The M13 Phage Assembly Machine Has a Membrane-Spanning Oligomeric Ring Structure. Viruses 2022; 14:v14061163. [PMID: 35746635 PMCID: PMC9228878 DOI: 10.3390/v14061163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 05/18/2022] [Accepted: 05/20/2022] [Indexed: 02/04/2023] Open
Abstract
Bacteriophage M13 assembles its progeny particles in the inner membrane of the host. The major component of the assembly machine is G1p and together with G11p it generates an oligomeric structure with a pore-like inner cavity and an ATP hydrolysing domain. This allows the formation of the phage filament, which assembles multiple copies of the membrane-inserted major coat protein G8p around the extruding single-stranded circular DNA. The phage filament then passes through the G4p secretin that is localized in the outer membrane. Presumably, the inner membrane G1p/G11p and the outer G4p form a common complex. To unravel the structural details of the M13 assembly machine, we purified G1p from infected E. coli cells. The protein was overproduced together with G11p and solubilized from the membrane as a multimeric complex with a size of about 320 kDa. The complex revealed a pore-like structure with an outer diameter of about 12 nm, matching the dimensions of the outer membrane G4p secretin. The function of the M13 assembly machine for phage generation and secretion is discussed.
Collapse
|
3
|
Braun R, Schönberger N, Vinke S, Lederer F, Kalinowski J, Pollmann K. Application of Next Generation Sequencing (NGS) in Phage Displayed Peptide Selection to Support the Identification of Arsenic-Binding Motifs. Viruses 2020; 12:E1360. [PMID: 33261041 PMCID: PMC7759992 DOI: 10.3390/v12121360] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 11/16/2020] [Accepted: 11/24/2020] [Indexed: 11/21/2022] Open
Abstract
Next generation sequencing (NGS) in combination with phage surface display (PSD) are powerful tools in the newly equipped molecular biology toolbox for the identification of specific target binding biomolecules. Application of PSD led to the discovery of manifold ligands in clinical and material research. However, limitations of traditional phage display hinder the identification process. Growth-based library biases and target-unrelated peptides often result in the dominance of parasitic sequences and the collapse of library diversity. This study describes the effective enrichment of specific peptide motifs potentially binding to arsenic as proof-of-concept using the combination of PSD and NGS. Arsenic is an environmental toxin, which is applied in various semiconductors as gallium arsenide and selective recovery of this element is crucial for recycling and remediation. The development of biomolecules as specific arsenic-binding sorbents is a new approach for its recovery. Usage of NGS for all biopanning fractions allowed for evaluation of motif enrichment, in-depth insight into the selection process and the discrimination of biopanning artefacts, e.g., the amplification-induced library-wide reduction in hydrophobic amino acid proportion. Application of bioinformatics tools led to the identification of an SxHS and a carboxy-terminal QxQ motif, which are potentially involved in the binding of arsenic. To the best of our knowledge, this is the first report of PSD combined with NGS of all relevant biopanning fractions.
Collapse
Affiliation(s)
- Robert Braun
- Department of Biotechnology, Helmholtz Institute Freiberg for Resource Technology, Helmholtz Center Dresden-Rossendorf, 01328 Dresden, Germany; (N.S.); (F.L.); (K.P.)
| | - Nora Schönberger
- Department of Biotechnology, Helmholtz Institute Freiberg for Resource Technology, Helmholtz Center Dresden-Rossendorf, 01328 Dresden, Germany; (N.S.); (F.L.); (K.P.)
| | - Svenja Vinke
- Microbial Genomics and Biotechnology, CeBiTec–Center for Biotechnology, Bielefeld University, 33594 Bielefeld, Germany; (S.V.); (J.K.)
| | - Franziska Lederer
- Department of Biotechnology, Helmholtz Institute Freiberg for Resource Technology, Helmholtz Center Dresden-Rossendorf, 01328 Dresden, Germany; (N.S.); (F.L.); (K.P.)
| | - Jörn Kalinowski
- Microbial Genomics and Biotechnology, CeBiTec–Center for Biotechnology, Bielefeld University, 33594 Bielefeld, Germany; (S.V.); (J.K.)
| | - Katrin Pollmann
- Department of Biotechnology, Helmholtz Institute Freiberg for Resource Technology, Helmholtz Center Dresden-Rossendorf, 01328 Dresden, Germany; (N.S.); (F.L.); (K.P.)
| |
Collapse
|
4
|
Abstract
To identify the translocation components in cells, and to understand how they function in protein transport and membrane insertion, a variety of techniques have been used such as genetics, biochemistry, structural biology and single molecule methods. In particular, site-directed crosslinking between the client proteins and components of the translocation machineries have contributed significantly in the past and will do so in the future. One advantage of this technology is that it can be applied in vivo as well as in vitro and a comparison of the two approaches can be made. Also, the in vivo techniques allow time-dependent protocols which are essential for studying cellular pathways. Protein purification and reconstitution into proteoliposomes are the gold standard for studying membrane-based transport and translocation systems. With these biochemically defined approaches the function of each component in protein transport can be addressed individually with a plethora of biophysical techniques. Recently, the use of nanodiscs for reconstitution has added another extension of this reductionistic approach. Fluorescence based studies, cryo-microscopy and NMR spectroscopy have significantly added to our understanding how proteins move into and across membranes and will do this also in future.
Collapse
Affiliation(s)
- Andreas Kuhn
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599, Stuttgart, Germany.
| |
Collapse
|
5
|
Hay ID, Lithgow T. Filamentous phages: masters of a microbial sharing economy. EMBO Rep 2019; 20:e47427. [PMID: 30952693 PMCID: PMC6549030 DOI: 10.15252/embr.201847427] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 01/30/2019] [Accepted: 03/19/2019] [Indexed: 12/11/2022] Open
Abstract
Bacteriophage ("bacteria eaters") or phage is the collective term for viruses that infect bacteria. While most phages are pathogens that kill their bacterial hosts, the filamentous phages of the sub-class Inoviridae live in cooperative relationships with their bacterial hosts, akin to the principal behaviours found in the modern-day sharing economy: peer-to-peer support, to offset any burden. Filamentous phages impose very little burden on bacteria and offset this by providing service to help build better biofilms, or provision of toxins and other factors that increase virulence, or modified behaviours that provide novel motile activity to their bacterial hosts. Past, present and future biotechnology applications have been built on this phage-host cooperativity, including DNA sequencing technology, tools for genetic engineering and molecular analysis of gene expression and protein production, and phage-display technologies for screening protein-ligand and protein-protein interactions. With the explosion of genome and metagenome sequencing surveys around the world, we are coming to realize that our knowledge of filamentous phage diversity remains at a tip-of-the-iceberg stage, promising that new biology and biotechnology are soon to come.
Collapse
Affiliation(s)
- Iain D Hay
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Trevor Lithgow
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, Vic., Australia
| |
Collapse
|
6
|
Loh B, Kuhn A, Leptihn S. The fascinating biology behind phage display: filamentous phage assembly. Mol Microbiol 2019; 111:1132-1138. [PMID: 30556628 DOI: 10.1111/mmi.14187] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
With the recently awarded Nobel Prize to the inventor of Phage Display, George Smith, the technique has once more gained attention. However, one should not forget about the biology behind the method. Almost always ignored is how the structure of this bacterial virus is assembled. In contrast to lytic phages, filamentous phages are constantly being extruded through the bacterial membranes without lysis. Such filamentous phages are found in all aquatic environments, such as rivers and lakes, in the deep sea, in arctic ice, in hot springs and, associated with their hosts, in plants and animals including humans. While most filamentous phages infect Gram-negative hosts, inoviruses of Gram-positive hosts have also been described. Despite being among the minority within the phage family with an estimate of less than 5%, filamentous phages are real parasites as they exist at the expense of the host, but do not kill it. In contrast to lytic bacteriophages, filamentous phages are assembled in the host's membrane and extruded across the cellular envelope while the bacterium continues to grow. In this review, we focus on this complex and yet poorly understood process of assembly and secretion of filamentous phages.
Collapse
Affiliation(s)
- Belinda Loh
- Zhejiang University School of Medicine, Zhejiang University-Edinburgh University (ZJU-UoE) Institute, International Campus, Zhejiang University, 718 East Haizhou Road, Haining, Zhejiang, 314400, P.R. China
| | - Andreas Kuhn
- Institute of Microbiology, University of Hohenheim, Garbenstrasse 30, Stuttgart, 70599, Germany
| | - Sebastian Leptihn
- Zhejiang University School of Medicine, Zhejiang University-Edinburgh University (ZJU-UoE) Institute, International Campus, Zhejiang University, 718 East Haizhou Road, Haining, Zhejiang, 314400, P.R. China
| |
Collapse
|
7
|
Qureshi T, Goto NK. Impact of Differential Detergent Interactions on Transmembrane Helix Dimerization Affinities. ACS OMEGA 2016; 1:277-285. [PMID: 31457129 PMCID: PMC6640775 DOI: 10.1021/acsomega.6b00138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 08/18/2016] [Indexed: 06/10/2023]
Abstract
Interactions between transmembrane (TM) helices play a critical role in the fundamental processes required for cells to communicate and exchange materials with their surroundings. Our understanding of the factors that promote TM helix interactions has greatly benefited from our ability to study these interactions in the solution phase through the use of membrane-mimetic micelles. However, less is known about the potential influence of juxtamembrane regions flanking the interacting TM helices that may modulate dimerization affinities, even when the interacting surface itself is not altered. To investigate this question, we used solution NMR to quantitate the dimerization affinity of the major coat protein from the M13 bacteriophage in sodium dodecyl sulfate (SDS), a well-characterized model of a single-spanning self-associating TM protein. Here, we showed that a shorter construct lacking the N-terminal amphipathic helix has a higher dimerization affinity relative to that of the full-length protein, with no change in the helical structure between the monomeric and dimeric states in both cases. Although this translated into a 0.6 kcal/mol difference in free energy when the SDS solvent was approximated as a continuous phase, there were deviations from this model at high protein to detergent ratios. Instead, the equilibria were better fit to a model that treats the empty micelle as an active participant in the reaction, giving rise to standard free energies of association that were the same for both full-length and TM-segment constructs. According to this model, the higher apparent affinity of the shorter peptide could be completely explained by the enhanced detergent binding by the monomer relative to that bound by the dimer. Therefore, differential detergent binding between the monomeric and dimeric states provides a mechanism by which TM helix interactions can be modulated by noninteracting juxtamembrane regions.
Collapse
|
8
|
Marvin DA, Symmons MF, Straus SK. Structure and assembly of filamentous bacteriophages. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 114:80-122. [PMID: 24582831 DOI: 10.1016/j.pbiomolbio.2014.02.003] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Accepted: 02/09/2014] [Indexed: 12/24/2022]
Abstract
Filamentous bacteriophages are interesting paradigms in structural molecular biology, in part because of the unusual mechanism of filamentous phage assembly. During assembly, several thousand copies of an intracellular DNA-binding protein bind to each copy of the replicating phage DNA, and are then displaced by membrane-spanning phage coat proteins as the nascent phage is extruded through the bacterial plasma membrane. This complicated process takes place without killing the host bacterium. The bacteriophage is a semi-flexible worm-like nucleoprotein filament. The virion comprises a tube of several thousand identical major coat protein subunits around a core of single-stranded circular DNA. Each protein subunit is a polymer of about 50 amino-acid residues, largely arranged in an α-helix. The subunits assemble into a helical sheath, with each subunit oriented at a small angle to the virion axis and interdigitated with neighbouring subunits. A few copies of "minor" phage proteins necessary for infection and/or extrusion of the virion are located at each end of the completed virion. Here we review both the structure of the virion and aspects of its function, such as the way the virion enters the host, multiplies, and exits to prey on further hosts. In particular we focus on our understanding of the way the components of the virion come together during assembly at the membrane. We try to follow a basic rule of empirical science, that one should chose the simplest theoretical explanation for experiments, but be prepared to modify or even abandon this explanation as new experiments add more detail.
Collapse
Affiliation(s)
- D A Marvin
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK.
| | - M F Symmons
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - S K Straus
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada.
| |
Collapse
|
9
|
Neugebauer SA, Baulig A, Kuhn A, Facey SJ. Membrane Protein Insertion of Variant MscL Proteins Occurs at YidC and SecYEG of Escherichia coli. J Mol Biol 2012; 417:375-86. [DOI: 10.1016/j.jmb.2012.01.046] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 12/23/2011] [Accepted: 01/26/2012] [Indexed: 10/14/2022]
|
10
|
Klenner C, Kuhn A. Dynamic disulfide scanning of the membrane-inserting Pf3 coat protein reveals multiple YidC substrate contacts. J Biol Chem 2011; 287:3769-76. [PMID: 22179606 DOI: 10.1074/jbc.m111.307223] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The membrane insertase YidC inserts newly synthesized proteins into the plasma membrane. While defects in YidC homologs in animals and plants cause diseases, YidC in bacteria is essential for life. Membrane insertion and assembly of ATP synthase and respiratory complexes is catalyzed by YidC. To investigate how YidC interacts with membrane-inserting proteins, we generated single cysteine mutants in YidC and in the model substrate Pf3 coat protein. The single cysteine mutants were expressed and analyzed for disulfide formation during 30 s of synthesis. The results show that the substrate contacts different YidC residues in four of the six transmembrane regions. The residues are located either in the region of the inner leaflet, in the center, as well as in the periplasmic leaflet, consistent with the hypothesis that YidC presents a hydrophobic platform for inserting membrane proteins. In a YidC mutant where most of the contacting residues were mutated to serines, YidC function was severely disturbed and no longer active in a complementation test, suggesting that the residues are important for function. In addition, a Pf3 mutant with a defect in membrane insertion was deficient to contact the periplasmic residues of YidC.
Collapse
Affiliation(s)
- Christian Klenner
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | | |
Collapse
|
11
|
Ploss M, Kuhn A. Membrane insertion and assembly of epitope-tagged gp9 at the tip of the M13 phage. BMC Microbiol 2011; 11:211. [PMID: 21943062 PMCID: PMC3193035 DOI: 10.1186/1471-2180-11-211] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 09/26/2011] [Indexed: 11/18/2022] Open
Abstract
Background Filamentous M13 phage extrude from infected Escherichia coli with a tip structure composed of gp7 and gp9. This tip structure is extended by the assembly of the filament composed of the major coat protein gp8. Finally, gp3 and gp6 terminate the phage structure at the proximal end. Up to now, gp3 has been the primary tool for phage display technology. However, gp7, gp8 and gp9 could also be used for phage display and these phage particles should bind to two different or more surfaces when the modified coat proteins are combined. Therefore, we tested here if the amino-terminal end of gp9 can be modified and whether the modified portion is exposed and detectable on the M13 phage particles. Results The amino-terminal region of gp9 was modified by inserting short sequences that encode antigenic epitopes. We show here that the modified gp9 proteins correctly integrate into the membrane using the membrane insertase YidC exposing the modified epitope into the periplasm. The proteins are then efficiently assembled onto the phage particles. Also extensions up to 36 amino acid residues at the amino-terminal end of gp9 did not interfere with membrane integration and phage assembly. The exposure of the antigenic tags on the phage was visualised with immunogold labelling by electron microscopy and verified by dot blotting with antibodies to the tags. Conclusions Our results suggest that gp9 at the phage tip is suitable for the phage display technology. The modified gp9 can be supplied in trans from a plasmid and fully complements M13 phage with an amber mutation in gene 9. The modified phage tip is very well accessible to antibodies.
Collapse
Affiliation(s)
- Martin Ploss
- Institute of Microbiology and Molecular Biology, University of Hohenheim, Stuttgart, Germany
| | | |
Collapse
|
12
|
Keller RCA. New user-friendly approach to obtain an Eisenberg plot and its use as a practical tool in protein sequence analysis. Int J Mol Sci 2011; 12:5577-91. [PMID: 22016610 PMCID: PMC3189734 DOI: 10.3390/ijms12095577] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 08/22/2011] [Accepted: 08/22/2011] [Indexed: 12/26/2022] Open
Abstract
The Eisenberg plot or hydrophobic moment plot methodology is one of the most frequently used methods of bioinformatics. Bioinformatics is more and more recognized as a helpful tool in Life Sciences in general, and recent developments in approaches recognizing lipid binding regions in proteins are promising in this respect. In this study a bioinformatics approach specialized in identifying lipid binding helical regions in proteins was used to obtain an Eisenberg plot. The validity of the Heliquest generated hydrophobic moment plot was checked and exemplified. This study indicates that the Eisenberg plot methodology can be transferred to another hydrophobicity scale and renders a user-friendly approach which can be utilized in routine checks in protein–lipid interaction and in protein and peptide lipid binding characterization studies. A combined approach seems to be advantageous and results in a powerful tool in the search of helical lipid-binding regions in proteins and peptides. The strength and limitations of the Eisenberg plot approach itself are discussed as well. The presented approach not only leads to a better understanding of the nature of the protein–lipid interactions but also provides a user-friendly tool for the search of lipid-binding regions in proteins and peptides.
Collapse
Affiliation(s)
- Rob C A Keller
- Section Chemistry, Charlemagne College, Wilhelminastraat 13-15, 6524 AJ Nijmegen, The Netherlands; E-Mail: ; Tel.: +0031-243820460
| |
Collapse
|
13
|
Affiliation(s)
- Ross E. Dalbey
- The Ohio State University, Department of Chemistry, Columbus, Ohio 43210;
| | - Peng Wang
- The Ohio State University, Department of Chemistry, Columbus, Ohio 43210;
| | - Andreas Kuhn
- Institute of Microbiology and Molecular Biology, University of Hohenheim, 70599 Stuttgart, Germany;
| |
Collapse
|
14
|
Klenner C, Yuan J, Dalbey RE, Kuhn A. The Pf3 coat protein contacts TM1 and TM3 of YidC during membrane biogenesis. FEBS Lett 2008; 582:3967-72. [DOI: 10.1016/j.febslet.2008.10.044] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Revised: 10/08/2008] [Accepted: 10/10/2008] [Indexed: 11/15/2022]
|
15
|
Wu Y, Shih SCC, Goto NK. Probing the structure of the Ff bacteriophage major coat protein transmembrane helix dimer by solution NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:3206-15. [PMID: 17915191 DOI: 10.1016/j.bbamem.2007.08.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2007] [Revised: 08/08/2007] [Accepted: 08/09/2007] [Indexed: 01/04/2023]
Abstract
The transmembrane (TM) segment of the major coat protein from Ff bacteriophage has been extensively studied as an example of dimerization in detergent and lipid bilayer systems. However, almost all the information regarding this interaction has been gained through mutagenesis studies, with little direct structural information being available. To this end solution NMR has the potential to provide new insights into structure of the dimer. In order to evaluate the utility of this approach we have studied a selectively 15N-labeled peptide containing the TM segment of MCP (MCPTM) by solution NMR. This peptide was found to give rise to detergent concentration-dependent spectra that were assigned to monomeric and dimeric forms. The standard free energy of this interaction in SDS was estimated from these spectra and found to be consistent with weak but specific dimerization. In addition, similar spectra could be obtained in beta-octyl glucoside with intermolecular paramagnetic relaxation experiments demonstrating a parallel arrangement of TM helices in the dimer. In both detergents backbone chemical shift differences between monomeric and dimeric forms of MCPTM showed that the largest changes occur around its GXXXG motif. The resulting structural model is consistent with observations made for MCP mutants previously characterized in biological membranes, opening the door to detailed structural characterization of this form of MCP. These results also have general implications for the study of weakly interacting TM segments by solution NMR since the use of similar sample conditions should allow structural data to be accessed for oligomeric states from a wide range systems that undergo biologically relevant but weak associations in the membrane.
Collapse
Affiliation(s)
- Yanqiu Wu
- Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, ON, K1N 6N5 Canada
| | | | | |
Collapse
|