Crystallization and preliminary X-ray diffraction studies of the signal recognition particle receptor FtsY from Mycoplasma mycoides

The prokaryotic signal recognition particle (SRP) pathway comprises two proteins, Ffh and FtsY, homologous to the SRP54 and SRα proteins in the more complex eukaryotic system. All four proteins are part of a unique subfamily of GTPases. Four truncated versions of the 412 amino-acid FtsY receptor protein from Mycoplasma mycoides have been cloned, expressed in Escherichia coli and purified. Purified proteins from all constructs and the full-length FtsY protein were subjected to crystallization trials. Crystals were obtained for the construct which comprised residues 98–412 corresponding to the conserved NG-domain (residues 194–497 in E. coli). A native data set at 1.9 Å resolution has been collected at 100 K using synchrotron radiation. The crystals belong to the space group P2₁2₁2, with unit-cell parameters a = 68.7, b = 101.1, c = 42.5 Å and one molecule in the asymmetric unit.