title: Molecular cloning, expression and characterization of a serine proteinase inhibitor gene from Entamoeba histolytica.
abstract: Serine proteinase inhibitors (serpins) are irreversible suicide inhibitors of proteinases that regulate a wide range of biological processes, including pathogen evasion of the host defence system. We report the cloning and characterization of a gene encoding a serpin from the protozoan parasite Entamoeba histolytica (Ehserp) that may function in this manner. The protein encoded by Ehserp contains 371 amino acids with a predicted mass of 42.6 kDa. Antibodies to a 42 kDa recombinant Ehserp react specifically with two bands of 42 and 49 kDa in trophozoite extracts. Ehserp has a cytoplasmic localization and is secreted by trophozoites incubated in the presence of mammalian cells, but not by resting trophozoites. A panel of mammalian serine proteinases was screened, but none of them was inhibited by the recombinant Ehserp. In contrast, the 49 kDa Ehserp present in the secretion product (SP) of activated macrophages interacted with human neutrophil cathepsin G to form a complex resistant to sodium dodecyl sulphate. We discuss the nature of the 42 and 49 kDa Ehserp and the possible roles that Ehserp may play in the survival of the parasite inside the host.
authors.affiliation: Department of Molecular Microbiology, The Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, POB 9649, 31096 Haifa, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Riahi
authors.forename: Rama
authors.initials: R
authors.lastname: Siman-Tov
authors.forename: Serge
authors.initials: S
authors.lastname: Ankri
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D056649:Cathepsin G; D002403:Cathepsins / Q000378:metabolism; D003001:Cloning, Molecular; D006224:Cricetinae; D004748:Entamoeba histolytica / Q000235:genetics* / Q000472:pathogenicity; D005786:Gene Expression Regulation; D017125:Genes, Protozoan; D006801:Humans; D007526:Isoelectric Point; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009504:Neutrophils / Q000201:enzymology; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D015843:Serpins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D015800:Protozoan Proteins; D015842:Serine Proteinase Inhibitors; D015843:Serpins; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G