Preliminary X-ray diffraction study of a new crystal form of C-1027-AG, the apoprotein of the macromolecular antitumor antibiotic C-1027 from Streptomyces globisporus

A new crystal form of C-1027-AG, the apoprotein of the macromolecular antitumor antibiotic C-1027 isolated from Streptomyces globisporus was obtained by the vapor-diffusion procedure using lithium sulfate as a precipitant. In the present crystallization, it is noteworthy that large-sized single crystals successfully grew from very small droplets (less than 1.01 µl). The present crystals belong to the trigonal system, space group P3₁21 or P3₂21 with cell dimensions of a = b = 62.6 and c = 54.2 Å. Assuming that the asymmetric unit contains one molecule, the V_m value is calculated as 2.9 Å³ Da^-1. A total of 3654 independent reflections from two native crystals was obtained up to 2.5 Å resolution with synchrotron radiation, the merging R factor being 0.097.