Crystallization, preliminary X-ray analysis and biophysical characterization of HPr kinase/phosphatase of Mycoplasma pneumoniae

The Mycoplasma pneumoniae HPr kinase/phosphatase (HPrK/P) is a member of a large family of enzymes which are central to carbon regulation in Gram-positive bacteria. The full-length M. pneumonia HPrK/P was crystallized from solutions of polyethylene glycol 8000 and KCl or NaCl which also contained the non-hydrolysable ATP analog adenosine 5′-[β,γ-methylene]triphosphate (AMPPCP). The crystals belong to the orthorhombic space group P2₁2₁2₁, with unit-cell parameters a = 117.1, b = 127.7, c = 170.7 Å. A complete X-­ray intensity data set has been collected and processed to 2.50 Å resolution. The slow self-rotation function revealed the presence of a sixfold axis. Dynamic light-scattering (DLS) experiments indicated a molecular weight of 197 kDa for HPrK/P in the absence of AMPPCP and of 217 kDa in the presence of the ATP analog. Thus, the biophysical and crystallographic data suggest that HPrK/P is a functional hexamer that undergoes an ATP-binding-induced conformational change.