ИСТИНА

One of the most sophisticated aspects in the design of artificial antibodies is to provide for their proper catalytic function, which requires accurate structural information. Here, the results showing how the antibody domain structure affects its functionality, is presented. The previously designed organophosphate-metabolizing reactibody A17 has been re-engineered by replacing its constant j light chain by the l chain, and the A17 l X-ray structure has been solved at 1.95A. It has been found that the active center of A17 l, compared to A17j, is displaced, stabilized and becomes more rigid due to interdomain interactions involving the CDR loops from the VL and VH domains. These VL/VH domains also display lower mobility as was deduced from the atomic displacement parameters of the crystal structure. The Trp-L92 residue is flipped out to form a lid over the entrance to active center pocket. The antibody elbow angle is decreased to 126°, compared to 138° in A17j. These structural differences leads to subtle changes in catalytic efficiency and thermodynamic parameters determined with two organophosphate ligands, as well as in affinity for peptide substrates selected from combinatorial cyclic peptide library, between A17j and A17 l variants. Presented data will be of interest and relevance to researchers dealing with the design of antibodies with tailor-made functions.