Nucleoside diphosphate kinase of Trypanosoma brucei.

Nucleoside diphosphate kinase (NDPK) is a highly conserved, multifunctional enzyme. Its originally described function is the phosphorylation of nucleoside diphosphates to the corresponding triphosphates, using ATP as the phosphate donor and a high-energy phosphorylated histidine residue as the reaction intermediate. More recently, a host of additional functions of NDPK have been discovered. Some of these correlate with the capacity of NDPK to transphosphorylate other proteins, in a manner reminiscent of bacterial two-component systems. Other functions may be mediated by direct DNA-binding of NDPK. This study describes the identification of NDPK from the parasitic protozoon Trypanosoma brucei. The genome of this major disease agent contains a single gene for NDPK. The predicted amino acid sequence of the trypanosomal enzyme is highly conserved with respect to all other species. The protein is constitutively expressed and is present in procyclic and in bloodstream forms. Immunofluorescence and immuno-electron microscopy demonstrate that trypanosomal NDPK (TbNDPK) is predominantly localized in the cell nucleus. Histidine phosphorylation of TbNDPK is essentially resistant to the experimental compound LY266500, a potent inhibitor of histidine phosphorylation of trypanosomal succinyl coenzyme A synthase.