Crystallization and preliminary X-ray crystallographic studies of DesR, a thermosensing response regulator in a two-component signalling system from Streptococcus pneumoniae.

The response regulator DesR, which activates the transcription of the des gene by binding to a regulatory region, is essential for controlling the fluidity of membrane phospholipids. DesR from Streptococcus pneumoniae was overexpressed in Escherichia coli. The protein was purified and crystallized for structural analysis. Diffraction data were collected to 1.7 A resolution using synchrotron radiation and the crystals belonged to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 46.91, b = 71.38, c = 117.73 A. Assuming the presence of a dimer in the asymmetric unit, this corresponds to a V(M) of 2.21 A(3) Da(-1).

Overexpression, purification, and preliminary X-ray crystallographic analysis of human brain-type creatine kinase.

Creatine kinase (CK; E.C. 2.7.3.2) is an important enzyme that catalyzes the reversible transfer of a phosphoryl group from ATP to creatine in energy homeostasis. The brain-type cytosolic isoform of creatine kinase (BB-CK), which is found mainly in the brain and retina, is a key enzyme in brain energy metabolism, because high-energy phosphates are transferred through the creatine kinase/phosphocreatine shuttle system. The recombinant human BB-CK protein was overexpressed as a soluble form in Escherichia coli and crystallized at 22 degrees C using PEG 4000 as a precipitant. Native X-ray diffraction data were collected to 2.2 A resolution using synchrotron radiation. The crystals belonged to the tetragonal space group P43212, with cell parameters of a=b=97.963, c= 164.312 A, and alpha=beta=gamma=90 degrees. The asymmetric unit contained two molecules of CK, giving a crystal volume per protein mass (Vm) of 1.80 A3 Da-1 and a solvent content of 31.6%.