RESUMO
Ecotin is a potent inhibitor of family S1A serine peptidases, enzymes lacking in the protozoan parasite Leishmania major. Nevertheless, L. major has three ecotin-like genes, termed inhibitor of serine peptidase (ISP). ISP1 is expressed in vector-borne procyclic and metacyclic promastigotes, whereas ISP2 is also expressed in the mammalian amastigote stage. Recombinant ISP2 inhibited neutrophil elastase, trypsin and chymotrypsin with K(i)s between 7.7 and 83 nM. L. major ISP2-ISP3 double null mutants (Deltaisp2/3) were created. These grew normally as promastigotes, but were internalized by macrophages more efficiently than wild-type parasites due to the upregulation of phagocytosis by a mechanism dependent on serine peptidase activity. Deltaisp2/3 promastigotes transformed to amastigotes, but failed to divide for 48 h. Intracellular multiplication of Deltaisp2/3 was similar to wild-type parasites when serine peptidase inhibitors were present, suggesting that defective intracellular growth results from the lack of serine peptidase inhibition during promastigote uptake. Deltaisp2/3 mutants were more infective than wild-type parasites to BALB/c mice at the early stages of infection, but became equivalent as the infection progressed. These data support the hypothesis that ISPs of L. major target host serine peptidases and influence the early stages of infection of the mammalian host.
Assuntos
Leishmania major/imunologia , Leishmania major/patogenicidade , Macrófagos/parasitologia , Proteínas de Protozoários/metabolismo , Inibidores de Serina Proteinase/metabolismo , Sequência de Aminoácidos , Animais , Quimotripsina/antagonistas & inibidores , Deleção de Genes , Leishmaniose Cutânea/imunologia , Leishmaniose Cutânea/parasitologia , Elastase de Leucócito/antagonistas & inibidores , Camundongos , Camundongos Endogâmicos BALB C , Dados de Sequência Molecular , Fagocitose/imunologia , Proteínas de Protozoários/genética , Alinhamento de Sequência , Inibidores de Serina Proteinase/genética , Tripsina/metabolismoRESUMO
Pyrococcus furiosus protease I (PFPI) is a multimeric cysteine peptidase from P. furiosus. Genome analyses indicate that orthologues are present in rather few other organisms, including Dictyostelium discoideum and several bacteria, Archaea and plants. An open reading frame (ORF) coding for a PFPI-like protein (PFP1) was identified in Leishmania major and Leishmania mexicana and full-length spliced and polyadenylated PFP1 mRNA detected for both species. Vestiges of a PFPI-like gene could also be identified in Leishmania braziliensis and Leishmania infantum, but no ORF remains owing to the presence of frame-shifts and stop codons. No evidence for a PFPI-like gene could be found in the syntenic region of Trypanosoma brucei or Trypanosoma cruzi, raising the possibility that the PFPI-like genes were acquired by a lateral gene transfer event after the divergence of trypanosomes and Leishmania. The gene may have subsequently degenerated into a pseudogene in some Leishmania species, owing to the loss of relevant biological function. However, antibodies raised against L. mexicana recombinant protein detected PFP1 in promastigote extracts of L. major, but not in L. mexicana promastigote or amastigote extracts. The expression of PFP1 in L. major suggests that PFP1 might contribute to the disease tropism that distinguishes this Leishmania species from others.
Assuntos
Proteínas Arqueais/genética , Genes de Protozoários , Leishmania major/genética , Leishmania/genética , Peptídeo Hidrolases/genética , Pseudogenes , Proteínas Recombinantes de Fusão/genética , Sequência de Aminoácidos , Animais , Proteínas Arqueais/química , Dados de Sequência Molecular , Fases de Leitura Aberta , Peptídeo Hidrolases/química , Proteínas Recombinantes de Fusão/químicaRESUMO
An NAD(+)-dependent glutamate dehydrogenase (GDH; EC 1.4.1.24) was cloned from the ruminal ciliate protozoan, Entodinium caudatum. The gene had high sequence similarity to GDH genes from the Bacteroides (class)--a class of bacteria which is highly represented in the rumen. When expressed in Escherichia coli the enzyme had a high affinity for ammonia and alpha-ketoglutarate (apparent K(m) of 2.33 and 0.71 mM, respectively) and a low affinity for glutamate (apparent K(m) of 98 mM). GDH activity and GDH mRNA concentration were increased by incubating washed E. caudatum cells with ammonia and antibiotics. These results suggest that the GDH is an anabolic enzyme catalysing the assimilation of ammonia by E. caudatum in the rumen and that the gene was probably acquired by lateral gene transfer from a ruminal bacterium.
Assuntos
Cilióforos/enzimologia , Genes de Protozoários , Glutamato Desidrogenase/genética , Glutamato Desidrogenase/metabolismo , Sequência de Aminoácidos , Amônia/metabolismo , Animais , Bacteroides/genética , Sequência de Bases , Clonagem Molecular , DNA de Protozoário/química , DNA de Protozoário/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Regulação da Expressão Gênica , Transferência Genética Horizontal , Glutamato Desidrogenase/isolamento & purificação , Ácido Glutâmico/metabolismo , Ácidos Cetoglutáricos/metabolismo , Dados de Sequência Molecular , Filogenia , RNA Mensageiro/análise , RNA de Protozoário/análise , Proteínas Recombinantes/metabolismo , Homologia de Sequência de Aminoácidos , Especificidade por SubstratoRESUMO
The FK506-binding proteins (FKBs) represent ubiquitous enzymes that catalyze the rate-limiting peptidyl prolyl cis-trans isomerization step in protein folding. The nematode Caenorhabditis elegans has eight FKBs, three of which (FKB-3, -4, and -5) have dual peptidyl prolyl cis-trans isomerase (PPIase) domains, signal peptides and ER retention signals. PPIase activity has been detected for recombinant FKB-3. Both FKB-3 and -5 are expressed in the exoskeleton-synthesizing hypodermis with transcript peaks that correspond to the molting and collagen synthesis cycles. FKB-4 is expressed at a low level throughout development. No phenotypes were observed in deletion mutants in each of the secretory pathway FKBs. Combined triple and fkb-4, -5 double deletion mutants were however found to arrest at 12 degrees C, but developed normally at 15-25 degrees C. This cold-sensitive larval lethal effect was not maternally derived, occurred during embryogenesis, and could be rescued following the transgenic introduction of a wild type copy of either fkb-4 or fkb-5. The temperature-sensitive defects also affected molting, cuticle collagen expression, hypodermal seam cell morphology, and the structural integrity of the cuticular extracellular matrix. This study establishes that the secretory pathway FK506-binding PPIase enzymes are essential for normal nematode development, collagen biogenesis, and the formation of an intact exoskeleton under adverse physiological conditions.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Colágeno/metabolismo , Matriz Extracelular/metabolismo , Peptidilprolil Isomerase/deficiência , Proteínas de Ligação a Tacrolimo/deficiência , Animais , Animais Geneticamente Modificados , Caenorhabditis elegans/citologia , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Temperatura Baixa , Matriz Extracelular/patologia , Deleção de Genes , Muda/genéticaRESUMO
A novel protein disulfide isomerase gene, pdi-3, was isolated from the nematode Caenorhabditis elegans. This gene encodes an enzyme related to the ERp60 class of thioredoxin proteins and was found to exhibit unusual enzymatic properties. Recombinant protein displayed both disulfide bond isomerase activity and calcium-dependent transglutaminase-like cross-linking activity. The pdi-3 transcript was developmentally constitutively expressed, and the encoded protein is present in many tissues including the gut and the hypodermis. The nematode hypodermis synthesizes the essential collagenous extracellular matrix (ECM) called the cuticle. Transcript disruption via double-stranded RNA interference resulted in dramatic and specific synthetic phenotypes in several C. elegans mutant alleles with weakened cuticles: sqt-3(e2117), dpy-18(e364, ok162, and bx26). These nematodes displayed severe dumpy phenotypes and disrupted lateral alae, a destabilized cuticle and abnormal male and hermaphrodite tail morphologies. These defects were confirmed to be consistent with hypodermal seam cell abnormalities and corresponded with the severe disruption of a cuticle collagen. Wild type nematodes did not exhibit observable morphological defects; however, cuticle collagen localization was mildly disrupted following pdi-3 RNA interference. The unusual thioredoxin enzyme, protein disulfide isomerase-3, may therefore play a role in ECM assembly. This enzyme is required for the proper maintenance of post-embryonic body shape in strains with a weakened cuticle, perhaps through ECM stabilization via cross-linking activity, disulfide isomerase protein folding activity, protein disulfide isomerase chaperone activity, or via multifunctional events.