Characterization of Chitin Synthases from Entamoeba
| Autor: | Said-Fernández S, Ute Willhoeft, Frank Ebert, Eduardo Campos-Góngora, Egbert Tannich |
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| Rok vydání: | 2004 |
| Předmět: |
Genes
Protozoan Molecular Sequence Data Molecular cloning Microbiology Gene Expression Regulation Enzymologic Homology (biology) Entamoeba chemistry.chemical_compound Species Specificity Chitin parasitic diseases Animals Amino Acid Sequence Northern blot Cloning Molecular skin and connective tissue diseases Gene Chitin Synthase Base Sequence Sequence Homology Amino Acid integumentary system biology Gene Expression Regulation Developmental RNA DNA Protozoan biology.organism_classification Isoenzymes Transmembrane domain Biochemistry chemistry RNA Protozoan |
| Zdroj: | Protist. 155:323-330 |
| ISSN: | 1434-4610 |
| DOI: | 10.1078/1434461041844204 |
| Popis: | Summary A major component of the Entamoeba cyst wall is chitin, a homopolymer of β-(1,4)-linked N -acetyl-D-glucosamine. Polymerization of chitin requires the presence of active chitin synthases (CHS), a group of enzymes belonging to the family of β-glycosyl transferases. CHS have been described for fungi, insects, and nematodes; however, information is lacking about the structure and expression of this class of enzymes in protozoons such as Entamoeba . In this study, the primary structures of two putative E.histolytica CHS (EhCHS-1 and EhCHS-2) were determined by gene cloning and homologous proteins were identified in databases from E. dispar and the reptilian parasite E. invadens . The latter constitutes the widely used model organism for the study of Entamoeba cyst development. The two ameba enzymes revealed between 23% and 33% sequence similarity to CHS from other organisms with full conservation of all residues critically important for CHS activity. Interestingly, EhCHS-1 and EhCHS-2 differed substantially in their predicted molecular weights (73 kD vs. 114 kD) as well as in their isoelectric points (5.04 vs. 8.05), and homology was restricted to a central stretch of about 400amino acid residues containing the catalytic domain. Outside the catalytic domain, EhCHS-1 was predicted to have seven transmembrane helices (TMH) of which the majority is located within the C-terminal part, resembling the situation found in yeast; whereas, EhCHS-2 is structurally related to nematode or insect chitin synthases, as it contained 17 predicted TMHs of which the majority is located within the N-terminal part of the molecule. Northern blot analysis revealed that genes corresponding to CHS-1 and CHS-2 are not expressed in Entamoeba trophozoites, but substantial amounts of CHS-1 and CHS-2 RNA were present 4 to 8 hours after induction of cyst formation by glucose deprivation of E. invadens . The time-courses of expression differed slightly between the two ameba CHS genes, as in contrast to CHS-1 RNA, expression of CHS-2 RNA was more transient and no plateau was observed between 8 and 16 hours of encystation. However, both CHS RNAs were no longer detectable after 48hours when most of the cells had been transformed into mature cysts. |
| Databáze: | OpenAIRE |
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