Solution Structure of Interleukin-1β Bound To a Potential Therapeutic Antibody

2012-10-26T12:55:31Z (GMT) by Ian Craig Wilkinson
The ability of antibodies to bind to target proteins with high specificity makes them an important class of biotherapeutic. The minimal functional form of an antibody, a single chain Fv (scFv), consists of two variable domains joined by a linker. Many therapeutics are based on the larger Fab fragments, which consist of two variable and two constant domains. Detailed structural information for potential therapeutic antibody-target protein complexes could clearly provide valuable insights into their mechanisms of action and mode of binding, however, currently there are very few structures available and none determined by NMR-based methods. To date, the collection of detailed structural information for scFvs has been limited by the formation of domain-swapped dimers. This equilibrium results in the formation of almost 50% dimer at the concentrations required for NMR. However, the work reported here shows that the monomeric form can be stabilised when bound to its target protein, which has enabled NMR-based structural analysis. This has allowed triple resonance data to be collected for the first time for a scFv-target protein complex, enabling over 90% of the backbone resonances to be assigned. Collection of chemical shift perturbation data, intraresidue NOEs and backbone amide RDCs has enabled a homology model for the scFv IC8 to be refined and docked to the structure of its target protein IL-1β. This has produced a reliable and well defined structure for the scFv-IL-1β complex. Evidence has also been obtained for a reorientation of the two variable domains induced by IL-1β binding, which could reflect conformational changes associated with antibody signalling. This study demonstrates that NMR spectroscopy can be used to obtain detailed structural information for antibody-target protein complexes, providing valuable information that could be used in the design and selection of future therapeutic antibodies.

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