Purification, crystallization and preliminary crystallographic studies of a two fibronectin type-III domain segment from chicken tenascin encompassing the heparin- and contactin-binding regions

A fragment of chicken tenascin consisting of fibronectin type-III domains 5 and 6 has been expressed in Escherichia coli. After modifying a previously reported purification protocol, an electrophoretically homogeneous recombi nant protein was obtained from which various crystal forms could be grown u nder identical conditions. Only one form was suitable for structure determi nation. These crystals belong to space group P2(1), with unit-cell paramete rs a = 45.2, b = 57.9, c = 72.2 Angstrom, beta = 91.4 degrees, and diffract to at least 2.6 Angstrom resolution using synchrotron radiation. From dens ity measurements of the crystals, it was found that there are two molecules in the asymmetric unit. Diffraction data of native, two platinum-derivativ e and one palladium-derivative crystals were collected.