Terminal respiration in certain mammalian trypanosomes

Fulton, J. D.; Spooner, D. F.

doi:10.1016/0014-4894(59)90014-1

Cited by 72 publications

(14 citation statements)

References 34 publications

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“…The lethality for BF T. brucei upon KREN3 repression is puzzling since normal BFs, which rely on glycolysis, have less edited COII mRNA than PFs (2,14,15) and lack cytochrome c oxidase (complex IV) activity (16,44,51,52). Indeed, BF cytochrome c oxidase subunit 6 null mutants are viable (60).…”

Section: Discussionmentioning

confidence: 99%

RNA Editing in Trypanosoma brucei Requires Three Different Editosomes

Carnes

Trotter

Peltan

et al. 2008

Molecular and Cellular Biology

106

150

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Trypanosoma brucei has three distinct ϳ20S editosomes that catalyze RNA editing by the insertion and deletion of uridylates. Editosomes with the KREN1 or KREN2 RNase III type endonucleases specifically cleave deletion and insertion editing site substrates, respectively. We report here that editosomes with KREPB2, which also has an RNase III motif, specifically cleave cytochrome oxidase II (COII) pre-mRNA insertion editing site substrates in vitro. Conditional repression and mutation studies also show that KREPB2 is an editing endonuclease specifically required for COII mRNA editing in vivo. Furthermore, KREPB2 expression is essential for the growth and survival of bloodstream forms. Thus, editing in T. brucei requires at least three compositionally and functionally distinct ϳ20S editosomes, two of which distinguish between different insertion editing sites. This unexpected finding reveals an additional level of complexity in the RNA editing process and suggests a mechanism for how the selection of sites for editing in vivo is controlled.RNA editing recodes most of the mitochondrial mRNAs in trypanosomatids by the insertion and deletion of uridine nucleotides (U's) using information provided by guide RNAs (gRNAs) (58). RNA editing is developmentally regulated and is required for parasites that cycle between insect vector and mammalian host (54). Proteins that perform catalytic steps of RNA editing have been identified: endonucleases KREN1 or KREN2 cleave at deletion or insertion sites, respectively; terminal uridylyl transferase (TUTase) KRET2 adds U's at insertion sites; U specific exoribonuclease (exoUase) KREX1 removes U's at deletion sites; and ligases KREL1 or KREL2 rejoin mRNA fragments after U addition or removal (5,13,25,30,34,55,61). These catalytic steps are coordinated by the multiprotein editosomes that sediment at ϳ20S on glycerol gradients (9, 43). KREPB2 was identified as an editosome component by mass spectrometry, and found to contain an RNase III motif harboring amino acids that are critical for catalysis, a U1 Zn 2ϩ finger, and double-stranded RNA binding. It has sequence similarity to KREN1 and KREN2, which also contain these three motifs (23,41,64). These data strongly suggest an RNA editing endonuclease role for KREPB2.KREN1 and KREN2 were shown to be RNA editing endonucleases using both RNA interference (RNAi) and conditional knockout cell lines (5, 61). Both KREN1 and KREN2 are essential for the normal growth of PF and BF cells, and repression of their expression by either method led to dramatic growth defects or death, respectively. Such repression of KREN1 eliminated in vitro cleavage by ϳ20S editosomes of a deletion site in a synthetic substrate modeled on ATPase subunit 6 (A6) pre-mRNA but did not alter cleavage of an insertion site in a substrate derived from the same mRNA. These studies and other data have shown that KREN1 is an editing endonuclease with a preference for sites from which U's are deleted (29). Similarly, repression of KREN2 eliminated in vitro cleavage at insertion ed...

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Section: Discussionmentioning

confidence: 99%

RNA Editing in Trypanosoma brucei Requires Three Different Editosomes

Carnes

Trotter

Peltan

et al. 2008

Molecular and Cellular Biology

106

150

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“…congolense degrades glucose beyond the pyruvic acid stage and produces appreciable quantities of carbon dioxide as well as acetic and succinic acids ( 1, 37), but a functional tricarboxylic acid cycle is probably not present. Reports of cyanide sensitivity implicating cytochrome oxidase involvement in terminal respiration, and claims that cytochrome pigment tectable by spectroscopy, should perhaps be tre some reservation (14). The "stickiness" of T .…”

Section: Discussionmentioning

confidence: 99%

“…The proximal end of the basal body is open (Figs. 14,16). Between the distal end of the intracytoplasmic basal body and the origin of the axoneme lies a largely extracytoplasmic transitional zone (Figs.…”

Section: Electron Microscopymentioning

confidence: 99%

“…Between the distal end of the intracytoplasmic basal body and the origin of the axoneme lies a largely extracytoplasmic transitional zone (Figs. 13,14,16) in which the peripheral triplets are replaced by doublets and each doublet is linked to the surface membrane of the flagellum by a partition-like connective. In the short intracytoplasmic transitional zone spoke-like fibres radiate from the doublets (Fig.…”

Section: Electron Microscopymentioning

confidence: 99%

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The Fine Structure of Trypanosoma congolense in Its Bloodstream Phase

Vickerman

1969

The Journal of Protozoology

118

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SYNOPSIS. The fine structure of 2 isolates of Trypanosoma congolense maintained in laboratory rodents has been studied from thin sections of osmium‐ and aldehyde‐fixed flagellates. The pellicular complex, nucleus, and flagellar apparatus are all similar to those of other African trypanosomes. Aberrant intracellular differentiation of the flagellum is occasionally found. As in bloodstream forms of other salivarian trypanosomes the single mitochondrion forms an irregular canal running from one end of the body to the other, with a shallow bowl‐shaped expansion forming a capsule for the fibrous kinetoplast (mitochondrial DNA). A connexion between the mitochondrial envelope of the kinetoplast and the basal body of the flagellum is not evident, and sometimes the flagellum base is not even apposed to the kinetoplast but lies behind it. Tubular cristae are present in the mitochondrial canal and, by light microscopy, this structure gives a positive reaction for NAD diaphorase suggesting at least some activity in electron transport, even tho at this stage in its life cycle respiration is doubtfully sensitive to cyanide and cytochrome pigments are in all probability absent. The region of the cytoplasm between the nucleus and the flagellar pocket has all the trappings associated with secretory cells in higher animals, or with the secretion of surface structures in phytoflagellates. just behind the nucleus a limb of granular reticulum subtends a Colgi stack of flattened saccules with attendant vesicles. Close to the distal pole of the Golgi complex is a network of smooth‐membraned cisternae, termed here the agranular or secretory reticulum, which undergoes localized swelling with the accumulation of a secretory product to form large spherical sacs or vacuoles. These network‐linked vacuoles probably correspond to the post nuclear vacuole complex visible by light microscopy. From its apparent secretory function this complex is regarded here as being possibly an extension or derivative of the Golgi complex, the smooth‐membraned tubules lying alongside the 2 structures possibly representing a link between them. By analogy with phytoflagellates and the secretory cells of higher animals, it is suggested that the secretion is transported for discharge into the flagellar pocket by way of multivesicular bodies and smooth‐walled tubules or vesicles. Spiny pits in the wall of the flagellar pocket, and similar‐sized vesicles in the nearby cytoplasm, could be stages in either exocytosis of secretion or endocytosis (pinocytosis). It is tentatively suggested that the secretion may be the material from which the surface coat is formed. Neither a cytostome nor a contractile vacuole has been observed in T. congolense.

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“…Pyruvate kinase activity is 2.4 times that of the parent strain, while phosphophexose isomerase activity is 2.0 times that of the parent. PHI activity has been used extensively as a measure of the glycolytic activity in organisms such as trypanosomes (10,16) ; and in neoplastic cells (4). Thus one can conclude from these results that the variants are glycolytically growing respiratory-deficient strains.…”

Section: Strains Of S Aurels 599mentioning

confidence: 99%

Characterization of Gentamicin‐Resistant Respiratory‐Deficient (Res⁻) Variant Strains of Staphylococcus aureus

Lewis

Bharosay

et al. 1990

Microbiology and Immunology

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Exposure of sensitive cells of Staphylococcus aureus to concentrations of gentamicin higher than the minimal inhibitory concentration, results in the recovery of low level resistant strains with a greatly altered phenotype (variants). Because the phenotypic alteration in these strains is so great the expected diagnostic characterization of these variants as S. aureus is obscured. Starting with a geneticallymarked parent strain, a comprehensive cytological, physiological, morphological , genetic and biochemical analysis of the variants isolated from it was carried out. The genetic lineage of the variants to the parent was also established by DNA/DNA hybridization. Variants result from mutations in the hemin biosynthesis locus , the effect of which is to disrupt the synthesis of components of the electron transport system, lipid synthesis and selected nucleotide synthesis. Thus the strains are defective in aerobic and anaerobic respiration, (res-), in active transport of aminoglycosides (which confers low level resistance), export of characteristic exo-enzymes, and in cell wall composition and structure.

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Terminal respiration in certain mammalian trypanosomes

Cited by 72 publications

References 34 publications

RNA Editing in Trypanosoma brucei Requires Three Different Editosomes

RNA Editing in Trypanosoma brucei Requires Three Different Editosomes

The Fine Structure of Trypanosoma congolense in Its Bloodstream Phase

Characterization of Gentamicin‐Resistant Respiratory‐Deficient (Res⁻) Variant Strains of Staphylococcus aureus

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Terminal respiration in certain mammalian trypanosomes

Cited by 72 publications

References 34 publications

RNA Editing in Trypanosoma brucei Requires Three Different Editosomes

RNA Editing in Trypanosoma brucei Requires Three Different Editosomes

The Fine Structure of Trypanosoma congolense in Its Bloodstream Phase

Characterization of Gentamicin‐Resistant Respiratory‐Deficient (Res−) Variant Strains of Staphylococcus aureus

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Characterization of Gentamicin‐Resistant Respiratory‐Deficient (Res⁻) Variant Strains of Staphylococcus aureus