Crystallization and preliminary X-ray diffraction studies of the GhKCH2 motor domain: alteration of pH significantly improved the quality of the crystals.

GhKCH2, a member of the kinesin superfamily, is a plant-specific microtubule-dependent motor protein from cotton with the ability to bind to both microtubules and microfilaments. Here, the motor domain of GhKCH2 (GhKCH2MD; amino acids 371-748) was overexpressed in Escherichia coli, purified and crystallized using the sitting-drop vapour-diffusion method. The pH of the crystallization buffer was shown to have a significant effect on the crystal morphology and diffraction quality. The crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 60.7, b = 78.6, c = 162.8 Å, α = β = γ = 90°. The Matthews coefficient and solvent content were calculated as 2.27 Å(3) Da(-1) and 45.87%, respectively. X-ray diffraction data for GhKCH2MD were collected on beamline BL17U1 at Shanghai Synchrotron Radiation Facility and processed to 2.8 Å resolution.