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Structure of the complex of an Fab fragment of a neutralizing antibody with foot‐and‐mouth disease virus: positioning of a highly mobile antigenic loop
Author(s) -
Hewat Elizabeth A.,
Verdaguer Nuria,
Fita Ignacio,
Blakemore Wendy,
Brookes Sharon,
King Andrew,
Newman John,
Domingo Esteban,
Mateu Mauricio G.,
Stuart David I.
Publication year - 1997
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/16.7.1492
Subject(s) - biology , virology , foot and mouth disease virus , neutralizing antibody , antibody , aphthovirus , antigen , virus , fragment (logic) , antigenic variation , genetics , computer science , programming language
Data from cryo‐electron microscopy and X‐ray crystallography have been combined to study the interactions of foot‐and‐mouth disease virus serotype C (FMDV‐C) with a strongly neutralizing monoclonal antibody (mAb) SD6. The mAb SD6 binds to the long flexible GH‐loop of viral protein 1 (VP1) which also binds to an integrin receptor. The structure of the virus–Fab complex was determined to 30 Å resolution using cryo‐electron microscopy and image analysis. The known structure of FMDV‐C, and of the SD6 Fab co‐crystallized with a synthetic peptide corresponding to the GH‐loop of VP1, were fitted to the cryo‐electron microscope density map. The SD6 Fab is seen to project almost radially from the viral surface in an orientation which is only compatible with monovalent binding of the mAb. Even taking into account the mAb hinge and elbow flexibility, it is not possible to model bivalent binding without severely distorting the Fabs. The bound GH‐loop is essentially in what has previously been termed the ‘up’ position in the best fit Fab orientation. The SD6 Fab interacts almost exclusively with the GH‐loop of VP1, making very few other contacts with the viral capsid. The position and orientation of the SD6 Fab bound to FMDV‐C is in accord with previous immunogenic data.