STUDIES ON UBIQUITIN RELATED MODIFIER 1 URM1 A POST TRANSLATIONAL MODIFICATION MACHINERY IN LEISHMANIA DONOVANI

Abstract

The present piece of work is the first study that characterizes the Leishmania specific ubiquitin related modifier-1 (LdUrm1) and its conjugation pathway in Leishmania donovani. Based on homology modelling we depicted that LdUrm1 possesses a and#946;-grasp fold and a C-terminal di-glycine motif unique to Ub/Ubls, essential for its conjugation to the target proteins. LdUrm1 also contains a pre-exposed di-glycine motif unlike other Ubls that need a C- terminal processing protease to expose the di-glycine motif that eventually lead to its conjugation to the proteinaceous targets in vivo. We identified LdUba4 as the E1 enzyme for LdUrm1 and its enzymatic activity was demonstrated in vitro by molybdenum blue based activity assay. The process was found to be energy dependent. Immuno-localisation studies showed that the LdUrm1 was localized at the anterior end near flagellar reservoir, in both promastigotes and axenic amastigotes. LdUba4 was found to be cytoplasmic. We demonstrated through Co-IP and subsequent immunoblotting that LdUrm1 and LdUba4 together form high molecular newline