title: Characterisation of a sexual stage-specific gene encoding ORC1 homologue in the human malaria parasite Plasmodium falciparum.
abstract: The origin recognition complex (ORC) is a multisubunit protein composed of six polypeptides that binds to replication origins and is essential for the initiation of chromosomal DNA replication. Using the Vectorette technique, we have isolated a novel gene encoding an ORC1-like protein from the human malaria parasite Plasmodium falciparum. The gene has no introns and encodes a protein (PfORC1) of 1189 amino acid residues with a predicted molecular mass of 139 kDa. PfORC1 contains all conserved sequences in the ORC1/Cdc6/Cdc18 family and displays the highest homology to the Schizosaccharomyces pombe ORC1. However, PfORC1 possesses an extensive N-terminal segment with several interesting features including multiple potential phosphorylation sites, a large proportion of charged amino acids, four copies of a heptamer repeat, two nuclear localisation signals, and a leucine zipper motif. Southern blot analyses show that the Pforc1 gene is present as a single copy per haploid genome and is located on chromosome 12. A 5600 nucleotide transcript of this gene is expressed predominantly in the sexual erythrocytic stage, indicating that PfORC1 may be involved in gametogenesis during which DNA is quickly replicated.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK. lij@cancer.org.uk
authors.forename: Ji-Liang
authors.initials: JL
authors.lastname: Li
authors.forename: Lynne S
authors.initials: LS
authors.lastname: Cox
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics* / Q000302:isolation & purification; D018507:Gene Expression Regulation, Developmental; D017125:Genes, Protozoan; D006801:Humans; D016778:Malaria, Falciparum / Q000469:parasitology; D008969:Molecular Sequence Data; D051738:Origin Recognition Complex; D010802:Phylogeny; D010963:Plasmodium falciparum / Q000235:genetics* / Q000254:growth & development* / Q000302:isolation & purification; D015800:Protozoan Proteins / Q000032:analysis / Q000235:genetics; D029702:Schizosaccharomyces pombe Proteins / Q000032:analysis; D016415:Sequence Alignment; D017385:Sequence Homology
chemical_list: D004268:DNA-Binding Proteins; C497223:ORC1 protein, human; D051738:Origin Recognition Complex; D015800:Protozoan Proteins; D029702:Schizosaccharomyces pombe Proteins; C064783:sexual stage specific protein, Plasmodium