title: Expression and characterization of human malaria parasite Plasmodium falciparum origin recognition complex subunit 1.
abstract: In eukaryotes, the origin recognition complex (ORC) is essential for the initiation of DNA replication. The largest subunit of this complex (ORC1) has a regulatory role in origin activation. Here we report the cloning and functional characterization of Plasmodium falciparum ORC1 homolog. Using immunofluorescence and immunoelectron microscopy, we show here that PfORC1 is expressed in the nucleus during the late trophozoite and schizont stages where maximum amount of DNA replication takes place. Homology modelling of the carboxy terminal region of PfORC1 (781-1033) using Saccharomyces pombe Cdc6/Cdc18 homolog as a template reveals the presence of a similar AAA+ type nucleotide-binding fold. This region shows ATPase activity in vitro that is important for the origin activity. To our knowledge, this is the first evidence of an individual ORC subunit that shows ATPase activity. These observations strongly suggest that PfORC1 might be involved in DNA replication initiation during the blood stage of the parasitic life cycle.
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 67, India.
authors.forename: Parul
authors.initials: P
authors.lastname: Mehra
authors.forename: Anup K
authors.initials: AK
authors.lastname: Biswas
authors.forename: Ashish
authors.initials: A
authors.lastname: Gupta
authors.forename: Samudrala
authors.initials: S
authors.lastname: Gourinath
authors.forename: Chetan E
authors.initials: CE
authors.lastname: Chitnis
authors.forename: Suman K
authors.initials: SK
authors.lastname: Dhar
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003198:Computer Simulation; D004912:Erythrocytes / Q000469:parasitology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006801:Humans; D016778:Malaria, Falciparum / Q000469:parasitology; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D051738:Origin Recognition Complex / Q000737:chemistry* / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000378:metabolism* / Q000472:pathogenicity; D015202:Protein Engineering / Q000379:methods*; D021122:Protein Subunits; D017386:Sequence Homology, Amino Acid
chemical_list: D051738:Origin Recognition Complex; D021122:Protein Subunits