Identification of a Functional Type IA Topoisomerase,LdTopIIIβ, from Kinetoplastid ParasiteLeishmania donovani

Abstract

DNA topoisomerases of kinetoplastids represent a family of DNA processing enzymes that essentially solve the topological problems not only in nuclear DNA but also in kinetoplast DNA. We have, for the first time, identified aLeishmania donovanihomologue of bacterial and eukaryotic IA type of topoisomerase III protein and termed asLdTopIIIβ. Complementation study of wild-type and mutantLdTopIIIβwith slow-growing topoisomerase III mutant yeastS. cerevisiaerevealed the functional conservation of the leishmanial counterpart of topoisomerase IIIβprotein, the 327 tyrosine being the active site amino acid. A C-terminal deletion construct ofLdTopIIIβcould not suppress the slow-growth phenotype of mutant yeast, indicating the requirement of C-terminal region for the enzyme functionin vivo.LdTopIIIβlocalized inside the nucleus and kinetoplast of the parasite. Taken together, our study indicates functional conservation and possible role ofLdTopIIIβin parasite DNA processing.