Purification, crystallization and preliminary X-ray analysis of the Fab fragment from MNAC13, a novel antagonistic anti-

The monoclonal antibody MNAC13 is a potent antagonist that prevents the binding of nerve-growth factor (NGF) to its tyrosine kinase A receptor (TrkA) in a variety of systems. Structural studies of the FabMNAC13 fragment were performed to gain insights into the mechanism of action of this potentially therapeutic monoclonal antibody. The optimal conditions for crystallization of FabMNAC13 were determined. Crystals appeared as prismatic bundles, displayed P212121 space-group symmetry and diffracted to a resolution of 1.8 Å. The unit-cell parameters were determined to be a = 52.73, b = 67.55, c = 111.43 Å. The data set was 99.5% complete. Molecular replacement was performed, resulting in a correlation coefficient of 0.55 and an R value of 0.40. The structure refinement is now in progress.