Structure of a nucleotide pyrophosphatase/phosphodiesterase (NPP) from Euphorbia characias latex characterized by small-angle X-ray scattering: clues for the general organization of plant NPPs

Little information is available concerning the structural features of nucleotide pyrophosphatase/phosphodiesterases (NPPs) of plant origin and the crystal structures of these proteins have not yet been reported. The aim of this study was to obtain insight into these aspects by carrying out a comparative analysis of the sequences of two different fragments of an NPP from the latex of the Mediterranean shrub Euphorbia characias (ELNPP) and by studying the low-resolution structure of the purified protein in solution by means of small-angle X-ray scattering. This is the first structure of a plant NPP in solution that has been reported to date. It is shown that the ELNPP sequence is highly conserved in many other plant species. Of note, the catalytic domains of these plant NPPs have the same highly conserved PDE-domain organization as mammalian NPPs. Moreover, ELNPP is a dimer in solution and this oligomerization state is likely to be common to other plant enzymes.