Crystallization and preliminary X-ray analysis of Saccharomyces cerevisiae Ypd1p, a key intermediate in phosphorelay signal transduction.

Ypd1p, a 167-residue protein from Saccharomyces cerevisiae, plays a key role in osmosensing phosphorelay signal transduction. It forms part of a multistep phosphorelay system which also includes Sln1p hybrid histidine kinase and two response regulators, Ssk1p and Skn7p. It has been overexpressed in soluble form in Escherichia coli with a His6-tag at its C-terminus. The recombinant protein has been crystallized at room temperature using ammonium sulfate and lithium sulfate as precipitants. Native diffraction data have been collected to 2.3 A using synchrotron radiation. The crystals are triclinic, belonging to the space group P1, with unit-cell parameters a = 65.78, b = 66.74, c = 65.75 A, alpha = 106.60, beta = 106.48, gamma = 115. 53 degrees. The asymmetric unit contains four molecules of the monomeric recombinant Ypd1p, with a corresponding Vm of 2.75 A3 Da-1 and a solvent content of 55.3%.