Crystallization and preliminary X-ray data analysis of the pXO1 plasmid-partitioning factor TubZ from Bacillus cereus

TubZ is a structural homologue of tubulin and FtsZ GTPases, which are involved in the type III plasmid-partitioning system. TubZ assembles into polymers in a GTP-dependent manner and drives plasmid segregation as `cytomotive' filaments. In this study, C-terminally truncated TubZ from Bacillus cereus was crystallized in the presence or absence of GDP by the hanging-drop vapour-diffusion method. The crystal of TubZ in complex with GDP belonged to the monoclinic space group P2₁, with unit-cell parameters a = 67.05, b = 84.49, c = 67.66 Å, β = 92.92°, and was non-isomorphous with GDP-bound TubZ previously crystallized in the presence of the slowly hydrolysable GTP analogue GTPγS. TubZ was also crystallized in the free form and the crystal belonged to space group P2₁, with unit-cell parameters a = 53.91, b = 65.54, c = 58.18 Å, β = 106.19°. Data were collected to 1.7 and 2.1 Å resolution for the free and GDP-bound forms, respectively.