Crystallization with Hapten of the Fab' Fragment from a Mouse IgA Myeloma Protein with Antidinitrophenyl Activity

Abstract

Abstract Protein 315, a mouse myeloma IgA protein which binds nitrophenyl ligands, and its pepsin-produced Fab' fragment have been purified by affinity chromatography. The Fab' fragments were found to be homogeneous by polyacrylamide electrophoresis and isoelectric focusing, and to possess a uniform binding constant. These fragments were readily crystallizable at low salt concentration near their isoelectric point (pH 4.7). Similarly crystals can be obtained of the Fab'-hapten complex. Such crystals have a 1:1 molar ratio of hapten (e, N-dinitrophenyl lysine) to protein.