CHYMOTRYPSINOGEN: A THREE-DIMENSIONAL FOURIER SYNTHESIS AT 5 å RESOLUTION

Abstract

Six heavy-atom -containing isomorphous derivatives of a new crystalline form of bovine chymotrypsinogen A have been prepared. On the basis of intensity changes observed in the X-ray diffraction patterns from these derivatives, phases of the parent reflections have been obtained out to a Bragg spacing of 5 A. Three-dimensional Fourier syntheses have been computed which reveal a molecule of approximately ellipsoidal shape, with axes 50, 40, and 40 A, but with an obvious hollow or depression. The chain conformation is complicated and appears to have little [alpha]-helix content in comparison with myoglobin and hemoglobin. It is not yet possible at this resolution to trace a continuous chain throughout the molecule.