Structure of tumour necrosis factor by X-ray solution scattering and preliminary studies by single crystal X-ray diffraction.

The structure of tumour necrosis factor has been investigated by X-ray small-angle scattering and X-ray diffraction using synchrotron radiation. The overall radius of gyration is 25.5 A. A plausible model accounting for the scattering curves consists of an elongated trimer with an axial ratio of 3 to 4 and a maximal chord with a lower limit of 80 A. Tumour necrosis factor has been crystallized in a trigonal space group. Our results are in favour of a single trimer in the asymmetric unit. The diffraction extends to 3.5 A.