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  • 1
    Electronic Resource
    Electronic Resource
    Anatomy of the antigenic structure of a large memberane autoantigen, the muscle-type nicotinic acetylcholine receptor (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Immunological reviews 163 (1998), S. 0 
    Details
    ISSN: 1600-065X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary: The neuromuscular junction nicotinic acetylcholine receptor (AChR), a pentameric membrane glycoprotein, is the autoantigen involved in the autoimmune disease myasthenia gravis (MG). In animals immunized with intact AChR and in human MG, the anti-AChR antibody response is polyclonal. However, a small extracellular region of the AChR a-subunit, the main immunogenic region (MIR), seems to be a major target for anti-AChR antibodies. A major loop containing overlapping epitopes for several anti-MIR monoclonal antibodies (mAbs) lies within residues α67–76 at the extreme synaptic end of each a-subunit; however, anti-MIR mAbs are functionally and structurally quite heterogeneous. Anti-MIR mAbs do not affect channel gating, but are very effective in the passive transfer of MG to animals; in contrast, their Fab or Fv fragments protect the AChR from the pathogenic effects of the intact antibodies. Antibodies against the cytoplas-mic region of the AChR can be elicited by immunization with denatured AChR and the precise epitopes of many such mAbs have been identified; however, it is unlikely that such antibodies are present in significant amounts in human MG. Antibodies to other extracellular epitopes on all AChR subunits are present in both experimental and human MG; these include antibodies to the acetylcholine-binding site which affect AChR function in various ways and also induce acute experimental MG. Finally, anti-AChR antibodies cross-reactive with noti-AChR antigens exist, suggesting that MG may result from molecular mimicry. Despite extensive studies, many gaps remain in our understanding of the antigenic structure of the AChR, especially in relation to human MG. A thorough understanding of the antigenic structure of the AChR is required for an in-depth understanding, and for possible specific immunotherapy, of MG.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-065X.1998.tb01190.x
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  • 2
    Electronic Resource
    Electronic Resource
    Isomerization of the Xaa-Pro peptide bond induced by ionic interactions of arginine (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 673-682 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Inclusion of Arg or Pro residues in proteins and peptides has been proved to play an essential role in biochemical functions through ionic interactions, conformational transitions, and formation of turns as well. In this study we present the conformational properties of the Ac-Arg-Ala-Pro (1), Ac-Arg-Ala-Pro-NH2 (2), Ac-Arg-Pro-Asp-NH2 (3), and Ac-Arg-Pro-Asp (4) tripeptides, using 1H-nmr spectroscopy and molecular dynamics. These peptides were modeled with the aim of studying the role of the Arg-guanidinium to carboxylate ionic interactions on the Xaa-Pro peptide bond isomerization. It was found with 1 and 4 that arginine preferentially interacts with the C-terminal carboxylate group, even though the β-carboxylate is also accessible. This tendency of the Arg moiety was found to induce the cis disposition of the Ala-Pro peptide bond in 1. It was also confirmed that the Arg…Asp side chain-side chain ionic interaction in 3 plays a key role in backbone folding and structural stabilization through a type I β-turn. The nmr pattern for 3 showed a remarkable similarity with that for various Arg-Tyr-Asp containing peptides, a sequence that is crucial for the adhesion properties of the Leishmania gp63 glycoprotein. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Concept and design of a new class of sequential oligopeptide carriers (SOC) for covalent attachment of multiple antigenic peptides (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 291-294 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Conformational requirements for molecular recognition of acetylcholine receptor main immunogenic region (MIR) analogues by monoclonal anti-MIR antibody: A two-dimensional nuclear magnetic resonance and molecular dynamics approach (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1123-1134 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational properties of two [D-A70, A76] and [Aib70, A76] analogues of the α67-76 Torpedo acetylcholine receptor fragment, with low binding capacity for the anti main immunogenic region (MIR) antibodies, were studied in DMSO by two-dimensional nmr techniques and molecular dynamics simulations. The results were compared to the free and bound conformations of the [A76] analogue, which has twice more affinity for the anti-MIR monoclonal antibody 6 (mAb6), than the natural Torpedo sequence. It appeared that a single substitution of the A70, at a crucial position, by the D-A70 or Aib70, could modify completely the conformational behavior of the peptide and reduced its recognition by the anti-MIR antibody. The WNPADY rigid structure at the N-terminal part was essential for antibody recognition. The adjacent more flexible C-terminal sequence (GGIK) gives additional stability to the monoclonal antibody-peptide complex probably due to an adequate orientation of the peptide side chains in the complex, by setting them in close contact with the antibody. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330714
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  • 5
    Electronic Resource
    Electronic Resource
    Compared structures of the free nicotinic acetylcholine receptor main immunogenic region (MIR) decapeptide and the antibody-bound [A76] MIR analogue: A molecular dynamics simulation from two-dimensional NMR data (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 419-432 
    Details
    ISSN: 0006-3525
    Keywords: acetylcholine receptor ; myasthenia gravis ; antigen-antibody interaction ; anti-genic peptide ; two-dimensional nmr ; molecular dynamics ; DMSO solvent box ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monoclonal antibodies against the main immunogenic region (MIR) of the muscle acetylcholine receptor (AChR) are capable of inducing experimental myasthenia gravis (MG) in animals. The epitope of these antibodies has been localized between residues 67 and 76 of the AChR α-subunit. The conformation in solution of the Torpedo californica MIR peptide and of its [A76] MIR analogue have been analyzed using molecular modeling based on nmr interproton distances and J-derived φ dihedral angles. Molecular dynamics simulations including dimethylsulfoxide as explicit solvent have been carried out on the free MIR peptide. Calculation of the structure of the [A76] MIR analogue bound to an anti-MIR monoclonal antibody have been performed in the presence of water molecules. A tightly folded structure appears for both peptides with a β-folded N-terminal N68-P-A-D71 sequence of type I in the free state and type III in the mAb6-bound state. The C-terminal sequence is folded in two different ways according to the result in the free and bound state of the peptides: two overlapping β / β or β / α turns result in a short helical sequence in the free MIR peptide, whereas the bound analogue is folded by an uncommon hydrogen bond closing an 11-membered cycle. This structural evolution is essentially the result of the reorientation of the hydrophobic side chains that are probably directly involved in peptide-antibody recognition. © 1997 John Wiley & Sons, Inc. Biopoly 40, 419-432, 1996
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Tr-Noe and MD studies of Leishmania gp63 SRYD-containing sequences bound to anti-SRYD monoclonal antibody (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 323-330 
    Details
    ISSN: 1573-3904
    Keywords: Antigen-antibody interaction ; Antigenic peptide ; Leishmania ; SRYD motif ; 2D NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The I250ASRYDQL257 synthetic octapeptideof the Leishmania major surface glycoproteingp63, which efficiently inhibits parasite attachmentto the macrophage receptors and mimics antigenicallyand functionally the RGDS sequence of fibronectin, wasstudied by 2D TR-NOESY in the presence of an anti-SRYDmonoclonal antibody (mAbSRYD) that recognizes bothSRYD-containing peptides and the cognate protein onintact parasites. Molecular modeling was performedusing distance constraints obtained from TR-NOEs. Thebound structure was compared with that of the freepeptide in DMSO solution and with the crystalstructure of the RYD fragment of the OPG2 Fab, anantireceptor antibody that mimics an RGD cell adhesion site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008896821140
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  • 7
    Electronic Resource
    Electronic Resource
    Design, synthesis and catalytic activity of a serine protease synthetic model (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 481-487 
    Details
    ISSN: 1573-3904
    Keywords: Catalytic triad residues ; Cyclic branched peptide ; Cyclization on solid support ; Enzymatic properties of serine protease model ; Proline cyclic hexapeptide ; Serine protease model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The design, synthesis and catalytic properties of acyclic branched peptide carrier that possesses thecatalytic triad residues of the serine proteases isreported. The synthesis of the peptide model wastotally completed on solid support using threedifferent orthogonal amino protecting groups.Hydrolytic activity measurements againstSuc-Ala-Ala-Ala-pNA substrate showed that it ishydrolysed by the peptide model to a small extent.Despite this small hydrolytic activity, it is thefirst time, to our knowledge, that hydrolysis of such a substrate is reported by an enzyme model compound.Contrary, this enzyme model peptide showedconsiderable activity against the Boc-Ala-pNPsubstrate (kcat = 0.414 min–1 and Km = 0.228 mm). These results suggest that thedesigned carrier brings in appropriate contact thecatalytic triad residues (Ser, His, Asp) resulting inthe obtained hydrolytic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008870113215
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  • 8
    Electronic Resource
    Electronic Resource
    TR-NOE and MD studies ofLeishmania gp63 SRYD-containing sequences bound to anti-SRYD monoclonal antibody (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 323-330 
    Details
    ISSN: 1573-3904
    Keywords: Antigen-antibody interaction ; Antigenic peptide ; Leishmania pg63 ; Molecular dynamics ; SRYD motif ; 2D NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The I250 ASRYDQL257 synthetic octapeptide of theLeishmania major surface glycoprotein gp63, which efficiently inhibits parasite attachment to the macrophage receptors and mimics antigenically and functionally the RGDS sequence of fibronectin, was studied by 2D TR-NOESY in the presence of an anti-SRYD monoclonal antibody (mAbSRYD) that recognizes both SRYD-containing peptides and the cognate protein on intact parasites. Molecular modeling was performed using distance constraints obtained from TR-NOEs. The bound structure was compared with that of the free peptide in DMSO solution and with the crystal structure of the RYD fragment of the OPG2 Fab, an antireceptor antibody that mimics an RGD cell adhesion site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02442896
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  • 9
    Electronic Resource
    Electronic Resource
    The PPGMRPP repetitive epitope of the Sm autoantigen: Antigenic specificity induced by conformational changes. Application of the Sequential Oligopeptide Carriers (SOCs) (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 447-454 
    Details
    ISSN: 1573-3904
    Keywords: Antigenicity of the Sm epitope ; Carriers of antigenic peptides ; Peptide conformation ; Proline-rich Sm epitope ; Sm autoantigen ; Systemic lupus erythematosus (SLE)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The PPGMRPP sequence, found in several copies in the Sm and U1RNP autoantigens, is the main target of anti-Sm and anti-U1RNP antibodies in systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) patient's sera. It is also recognized, to a lower extent, by anti-Ro/SSA and anti-La/SSB specificities. The PPGMRPP-NH2 peptide amide and the PPGMRPP peptide, which is bound to a pentameric sequential oligopeptide carrier (SOC5), were examined by1H-NMR spectroscopy and ELISA assays, using sera from patients with autimmune rheumatic diseases. Among the three main conformers found for the free PPGMRPP, the extended one was also identified for PPGMRPP-NH2 and (PPGMRPP)5-SOC5. This can be attributed to the absence of ionic interactions between the Arg-guanidinium and the carboxylate group in the amide and SOC5-bound forms of the peptide. Immunoassays using sera from various specificities showed an enhanced anti-Sm and anti-U1RNP recognition of PPGMRPP-NH2 and (PPGMRPP)5-SOC5, and lowering of the anti-Ro/SSA and anti-La/SSB reactivity. The presence of multiple conformers of free PPGMRPP may explain the unexpected cross-reactivity to the anti-Ro/La positive sera, while the prevalence of the extended conformation in PPGMRPP-NH2 and (PPGMRPP)5-SOC5 is mainly responsible for the enhanced recognition from the anti-Sm and anti-U1RNP autoantibodies. it is concluded that the antigenic specificity of PPGMRPP-NH2 and (PPGMRPP)5-SOC5 is mainly induced by conformational changes resulting from the conversion of the C-terminal carboxylate group to the amide form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02442915
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  • 10
    Electronic Resource
    Electronic Resource
    Conformational and antigenic properties of SRYD-containing peptide analogues of Leishmania gp63 adhesion site (1996)
    Springer
    International journal of peptide research and therapeutics 3 (1996), S. 200-208 
    Details
    ISSN: 1573-3904
    Keywords: Arginine ionic interactions ; gp63 adhesion site ; Arginine-aspartic acid interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The antigenicity and conformational properties of the Ser-Arg-Tyr-Asp (SRYD) segment (252–255) of the major surface glycoprotein ofLeishmania, gp63, which plays a key role in the parasite-macrophage attachement, are presented. It was found that the antibody recognition, using anti-IASRYDQL antibodies, of the SRYD-containing analogues, Ac-SRYD-NH2 (1), ANIASRYD-NH2 (2), Ac-SRYD (3), SRYD (4) and ANIASRYD (5), is rather similar. The structure of the SRYD moiety in analogues 1 and 2 is characterized by the presence of a type I β-turn, stabilized by the formation of a hydrogen bonding between the C-terminaltrans-carboxamide proton and the Arg-CO and an ionic bridge between arginine and aspartic acid side chains, while the conformation of compounds 3, 4 and 5 is stabilized by an ionic bridge between the arginine side chain and the C-terminal carboxylate group. A common structural motif involving the arginine side chain in an ionic interaction is identified in all the SRYD analogues, which may explain the observed similarities in the antibody recognition of the reported peptides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00128108
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