PhnP belongs to a 14-gene operon that supports the growth of Escherichia coli on alkylphosphonates as a sole source of phosphorus; however, the exact biochemistry of phosphonate degradation by this pathway is poorly understood. The protein was recombinantly expressed in Escherichia coli and purified to homogeneity. Sitting-drop vapour diffusion in combination with microseeding was used to obtain crystals that were suitable for X-ray diffraction. Data were collected to 1.3 A and the crystals belonged to space group C2, with unit-cell parameters a = 111.65, b = 75.41, c = 83.23 A, alpha = gamma = 90, beta = 126.3 degrees .