Crystallization and preliminary X-ray studies of SdiA from Escherichia coli.

SdiA enhances cell division by regulating the ftsQAZ operon in Escherichia coli as a transcription activator. In addition, SdiA is suggested to play a role in detecting quorum signals that emanate from other species. It is therefore a homologue of LuxR, a cognate quorum-sensing receptor that recognizes a quorum signal and activates the quorum responses. To elucidate the role of SdiA and its functional and structural relationship to LuxR, structural studies were performed on E. coli SdiA. Recombinant SdiA was overexpressed, purified and crystallized at 287 K using the hanging-drop vapour-diffusion method. X-ray diffraction data from a native crystal were collected with 99.7% completeness to 2.7 A resolution with an R(merge) of 6.0%. The crystals belong to the hexagonal space group P6(1)22 or P6(5)22, with unit-cell parameters a = b = 130.47, c = 125.23 A.