Feige, M.J.* ; Gräwert, M.A.* ; Marcinowski, M.* ; Hennig, J. ; Behnke, J.* ; Ausländer, D.* ; Herold, E.M.* ; Peschek, J.* ; Castro, C.D.* ; Flajnik, M.* ; Hendershot, L.M.* ; Sattler, M. ; Groll, M.* ; Buchner, J.*
     
    
        
         The structural analysis of shark IgNAR antibodies reveals evolutionary principles of immunoglobulins.
        The structural analysis of shark IgNAR antibodies reveals evolutionary principles of immunoglobulins.
     
    
        
    
    
        
        Proc. Natl. Acad. Sci. U.S.A. 111, 8155-8160 (2014)
    
    
    
      
      
	
	    Sharks and other cartilaginous fish are the phylogenetically oldest living organisms that rely on antibodies as part of their adaptive immune system. They produce the immunoglobulin new antigen receptor (IgNAR), a homodimeric heavy chain-only antibody, as a major part of their humoral adaptive immune response. Here, we report the atomic resolution structure of the IgNAR constant domains and a structural model of this heavy chain-only antibody. We find that despite low sequence conservation, the basic Ig fold of modern antibodies is already present in the evolutionary ancient shark IgNAR domains, highlighting key structural determinants of the ubiquitous Ig fold. In contrast, structural differences between human and shark antibody domains explain the high stability of several IgNAR domains and allowed us to engineer human antibodies for increased stability and secretion efficiency. We identified two constant domains, C1 and C3, that act as dimerization modules within IgNAR. Together with the individual domain structures and small-angle X-ray scattering, this allowed us to develop a structural model of the complete IgNAR molecule. Its constant region exhibits an elongated shape with flexibility and a characteristic kink in the middle. Despite the lack of a canonical hinge region, the variable domains are spaced appropriately wide for binding to multiple antigens. Thus, the shark IgNAR domains already display the well-known Ig fold, but apart from that, this heavy chain-only antibody employs unique ways for dimerization and positioning of functional modules.
	
	
	    
	
       
      
	
	    
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        Publication type
        Article: Journal article
    
 
    
        Document type
        Scientific Article
    
 
    
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        Keywords
        Antibody Structure ; Protein Engineering ; Protein Evolution ; Protein Folding; Chain Binding-protein; Heavy-chain; Antigen Receptor; Light-chain; Primordial Immunoglobulin; Cartilaginous Fish; Domain Antibodies; Constant Fragment; High-resolution; Common-core
    
 
    
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        Language
        english
    
 
    
        Publication Year
        2014
    
 
    
        Prepublished in Year
        
    
 
    
        HGF-reported in Year
        2014
    
 
    
    
        ISSN (print) / ISBN
        0027-8424
    
 
    
        e-ISSN
        1091-6490
    
 
    
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	    Volume: 111,  
	    Issue: 22,  
	    Pages: 8155-8160 
	    Article Number: ,  
	    Supplement: ,  
	
    
 
    
        
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            Publisher
            National Academy of Sciences
        
 
        
            Publishing Place
            Washington
        
 
	
        
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        Reviewing status
        Peer reviewed
    
 
     
    
        POF-Topic(s)
        30203 - Molecular Targets and Therapies
    
 
    
        Research field(s)
        Enabling and Novel Technologies
    
 
    
        PSP Element(s)
        G-503000-001
    
 
    
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        Erfassungsdatum
        2014-05-18