CONSTRUCTION AND CHARACTERIZATION OF A SINGLE-CHAIN CATALYTIC ANTIBODY

The antigen-binding (Fab) fragment of the catalytic monoclonal antibody NPN43C9 has recently been cloned by using bacteriophage-lambda. By inserting the variable regions of this Fab coding sequence into a (NH2)-V(L)-linker-V(H)-(COOH) construct (where V(L) and V(H) represent the heavy and light chain variable regions), we have assembled a recombinant gene encoding a catalytic single-chain antigen-binding protein. This protein has been expressed in Escherichia coli and exhibits the same catalytic parameters as the parent monoclonal antibody NPN43C9. Single-chain forms of catalytic antibodies may prove valuable for structural and site-directed mutagenesis studies as well as for large-scale applications of catalytic antibodies.