A general vector, pASK84, for cloning, bacterial production, and single-step purification of antibody F_ab fragments

The expression vector pASK84 was designed for the convenient cloning of immunoglobulin variable domain genes, as well as periplasmic secretion of the corresponding F_ab fragment in Escherichia coli. The plasmid provides the constant domain genes of mouse IgG1/K with a hexa-histidine tag fused to the C terminus of the heavy chain. This strategy enables the rapid and efficient purification of the functional recombinant F_ab fragment via immobilized metal affinity chromatography. The versatility of this expression and purification system is demonstrated using the variable domains of the well-characterized anti-lysozyme antibody D1.3.