Secreted variant of nucleoside diphosphate kinase from the intracellular parasitic nematode Trichinella spiralis

The molecular components involved in the survival of the parasitic nematode Trichinella spiralis in an intracellular environment are poorly characteri zed. Here we demonstrate that infective larvae secrete a nucleoside diphosp hate kinase when maintained in vitro. The secreted enzyme forms a phosphohi stidine intermediate and shows broad specificity in that it readily accepts gamma -phosphate from both ATP and GTP and donates it to all nucleoside an d deoxynucleoside diphosphate accepters tested. The enzyme,vas partially pu rified from culture medium by ATP affinity chromatography and identified as a 17-kDa protein by autophosphorylation and reactivity with an antibody to a plant-derived homologue. Secreted nucleoside diphosphate kinases have pr eviously been identified only in prokaryotic organisms, all of them bacteri al pathogens. The identification of a secreted variant of this enzyme from a multicellular eukaryote is very unusual and is suggestive of a role in mo dulating host cell function.