Crystallization and preliminary X-ray crystallographic studies of a macromolecular antitumour antibiotic, C1027.

C1027 is a macromolecular antitumour antibiotic produced by Streptomyces globispourus C1027 and consists of an apoprotein and a non-protein labile chromophore. Little is known about how the thermally unstable chromophore is stabilized by the apoprotein. The purified C1027 was monodisperse according to dynamic light-scattering measurements and crystallized in two different crystal forms from two different starting conditions using the vapour-diffusion method. Condition I yielded hexagonal prism crystals having space group P3(1)/P3(2) and unit-cell parameters a = b = 66.8, c = 55.4 A. Diffraction data were collected to 2.1 A resolution using an in-house Rigaku rotating Cu anode X-ray generator. Another condition produced rod-like crystals with space group P3(1)21/P3(2)21 and unit-cell parameters a = b = 55.15, c = 55.87 A. A data set to 1.8 A resolution was collected from a rod-like crystal using a MAR CCD detector at the SRS synchrotron source.