Preliminary X-ray diffraction studies of the transcriptional inhibitory antibody Fab41.4

The binding of transcription factor ATF-1 to DNA contributes to gene expres sion and regulation of cell growth. Antibody Mab41.4, raised against ATF-1, and its derivatives Fab41.4 and scFv41.4 inhibit specific DNA binding in v itro and induce apoptotic death of tumor cells in vivo. Structural studies of Fab41.4 were performed to gain insight into the mechanism of action of t his potentially therapeutic antibody. The optimal conditions for crystalliz ation of Fab41.4 were determined. Crystals were needle-like in appearance, displayed C2 space-group symmetry and diffracted to a resolution of 1.6 Ang strom. The unit-cell parameters were determined to be a = 186.64, b = 40.22 , c = 55.58 Angstrom, alpha = gamma = 90, beta = 96.93 degrees. The data se t was 97.7% complete. Molecular replacement was performed, resulting in an R value of 44.6%.