title: Protein phosphatase beta, a putative type-2A protein phosphatase from the human malaria parasite Plasmodium falciparum.
abstract: Protein phosphatases play a critical role in the regulation of the eukaryotic cell cycle and signal transduction. A putative protein serine/threonine phosphatase gene has been isolated from the human malaria parasite Plasmodium falciparum. The gene has an unusual intron that contains four repeats of 32 nucleotides and displays a high degree of size polymorphism among different strains of P. falciparum. The open reading frame reconstituted by removal of the intron encodes a protein of 466 amino acids with a predicted molecular mass of approximately 53.7 kDa. The encoded protein, termed protein phosphatase beta (PP-beta), is composed of two distinct domains. The C-terminal domain comprises 315 amino acids and exhibits a striking similarity to the catalytic subunits of the type-2A protein phosphatases. Database searches revealed that the catalytic domain has the highest similarity to Schizosaccharomyces pombe Ppa1 (58% identity and 73% similarity). However, it contains a hydrophilic insert consisting of five amino acids. The N-terminal domain comprises 151 amino acid residues and exhibits several striking features, including high levels of charged amino acids and asparagine, and multiple consensus phosphorylation sites for a number of protein kinases. An overall structural comparison of PP-beta with other members of the protein phosphatase 2A group revealed that PP-beta is more closely related to Saccharomyces cerevisiae PPH22. Southern blots of genomic DNA digests and chromosomal separations showed that PP-beta is a single-copy gene and is located on chromosome 9. A 2800-nucleotide transcript of this gene is expressed specifically in the sexual erythrocytic stage (gametocytes). The results indicate that PP-beta may be involved in sexual stage development.
authors.affiliation: Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, UK.
authors.forename: J L
authors.initials: JL
authors.lastname: Li
authors.forename: D A
authors.initials: DA
authors.lastname: Baker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D004912:Erythrocytes / Q000469:parasitology; D018507:Gene Expression Regulation, Developmental; D017125:Genes, Protozoan; D006801:Humans; D007438:Introns; D016778:Malaria, Falciparum / Q000469:parasitology; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D016133:Polymerase Chain Reaction; D054648:Protein Phosphatase 2; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D016054:DNA, Protozoan; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2