Molecular cloning, cell localization and binding affinity to DNA replication proteins of the p36/LACK protective antigen from Leishmania infantum

The p36/LACK antigen from Leishmania, an analogue of the receptor for activ ated protein kinase C (PKC), induces high levels of protection against para site infection in the BALB/c mouse model. This protection is more than twic e as high as that elicited by major parasite antigens such as soluble Leish mania antigen or the main surface protease gp63. We have cloned and purifie d p36/LACK from Leishmania infantum, the causative agent of visceral leishm aniasis in Europe. This protein belongs to the large family of WD 40 repeat proteins confined to eukaryotes and involved in numerous regulatory functi ons. Differential solubilization and immunofluorescence experiments indicat e that p36/LACK is present close to the kinetoplast disc in the cell cytopl asm, probably bound to multiprotein complexes but not to membrane structure s. These complexes probably also include cytoplasm PKC isoforms. The use of a genetically-encoded peptide library indicates that p36/LACK binds sequen ces present in several proteins involved in DNA replication and RNA synthes is. The recognition and binding sequences present in vacuolar proteins and at the beta-chain of major histocompatability complex (MHC) class II sugges t the involvement of this regulatory protein in the early mechanisms trigge ring the protective immune response of the host against the parasite infect ion.