Crystallization and preliminary X-Ray diffraction analysis of the 190-A-long coiled-coil dimerization domain of the actin-bundling protein cortexillin I from dictyostelium discoideum

We have crystallized the approximately 190-A-long parallel two-stranded coiled-coil oligomerization domain of the actin-bundling protein cortexillin I from Dictyostelium discoideum. The orthorhombic crystals belong to the space group C2221 with unit cell dimensions of a = 71.3 A, b = 127.8 A, and c = 91.6 A. As both native and selenomethionine-substituted protein crystals diffract to 3.0 and 2.85 A resolution, respectively, using synchrotron radiation, they are suitable for the first high-resolution structural analysis of a two-stranded coiled coil comprising more than six heptad repeats. Moreover, because the polypeptide chain fragment contains a recently identified two-heptad-repeat long sequence that is indispensable for the assembly of the cortexillin I coiled-coil oligomerization domain, its high-resolution structure should enable us to extend our knowledge on the molecular mechanisms underlaying coiled-coil formation and to establish the precise manner in which the two "trigger" sequences interact with one another in the dimer.