Trypanosoma cruzi arginine kinase characterization and cloning - A novel energetic pathway in protozoan parasites

This work contains the first description of a guanidino kinase in a flagell ar unicellular parasite. The enzyme phosphorylates L-arginine and was chara cterized in preparations from Trypanosoma cruzi, the ethiological agent of Chagas' disease. The activity requires ATP and a divalent cation. Under sta ndard assay conditions (1 mM L-arginine), the presence of B-fold higher con centrations of canavanine or histidine produced a greater than 50% enzyme i nhibition, The base sequence of this enzyme revealed an open reading frame of 357 amino acids and a molecular weight of 40,201. The amino acid sequenc e shows all of the characteristic consensus blocks of the ATP:guanidino pho sphotransferase family and a putative "actinin-type" actin-binding domain. The highest amino acid identities of the T. cruzi sequence, about 70%, were with arginine kinases from Arthropoda. Southern and chromosome blots revea led that the kinase is encoded by a single-copy gene. Moreover, Northern bl ot analysis showed an mRNA subpopulation of about 2.0 kilobases, and Wester n blotting of T. cruzi-soluble polypeptides revealed a 40-kDa band. The fin ding in the parasite of a phosphagen and its biosynthetic pathway, which ar e totally different from those in mammalian host tissues, points out this a rginine kinase as a possible chemotherapy target for Chagas' disease.