Characterization of a divergent glycosomal microbody phosphoglycerate kinase from Trypanosoma brucei

Alexander, Kenneth R.; Parsons, Marilyn

doi:10.1016/0166-6851(93)90137-m

Cited by 29 publications

(11 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…brucei and many other trypanosomatids have three genes encoding isozymes of phosphoglycerate kinase (PGK). The first, the A gene, is present in glycosomes in low relative abundance (2,210); preliminary data suggest that its signal sequence is somewhere within the N-terminal 91 amino acids (156). The B gene encodes a cytoplasmic enzyme, and the C VOL.…”

Section: Glycosomal Import Signalsmentioning

confidence: 99%

Protein trafficking in kinetoplastid protozoa.

Clayton¹,

Häusler²,

Blattner³

1995

Microbiological Reviews

View full text Add to dashboard Cite

Section: Glycosomal Import Signalsmentioning

confidence: 99%

Protein trafficking in kinetoplastid protozoa.

Clayton¹,

Häusler²,

Blattner³

1995

Microbiological Reviews

View full text Add to dashboard Cite

“…Although the three PGK genes are co-transcribed, they have different expression patterns (27). The PGKA protein and mRNA are present at low levels in the glycosomes of all life stages of the parasite (28,29). PGKB and PGKC have distinct expression patterns as follows.…”

mentioning

confidence: 99%

Control and Regulation of Gene Expression

Haanstra

Stewart

Luu

et al. 2008

Journal of Biological Chemistry

View full text Add to dashboard Cite

Isoenzymes of phosphoglycerate kinase in Trypanosoma brucei are differentially expressed in its two main life stages. This study addresses how the organism manages to make sufficient amounts of the isoenzyme with the correct localization, which processes (transcription, splicing, and RNA degradation) control the levels of mRNAs, and how the organism regulates the switch in isoform expression. For this, we combined new quantitative measurements of phosphoglycerate kinase mRNA abundance, RNA precursor stability, trans splicing, and ribosome loading with published data and made a kinetic computer model. For the analysis of regulation we extended regulation analysis. Although phosphoglycerate kinase mRNAs are present at surprisingly low concentrations (e.g. 12 molecules per cell), its protein is highly abundant. Substantial control of mRNA and protein levels was exerted by both mRNA synthesis and degradation, whereas splicing and precursor degradation had little control on mRNA and protein concentrations. Yet regulation of mRNA levels does not occur by transcription, but by adjusting mRNA degradation. The contribution of splicing to regulation is negligible, as for all cases where splicing is faster than RNA precursor degradation.The flux through a metabolic pathway depends on the kinetic characteristics and concentrations of the constituent enzymes, on the levels of co-enzymes, and on their compartmentation. The concentrations of the enzymes in turn depend on the rates of transcription, processing, nuclear export, translation, degradation of the mRNA, and protein processing and degradation. Because each of these levels can in principle be regulated, the challenge is how to analyze the behavior of such a complex system in terms of the underlying processes.Metabolic control analysis (MCA) 4 and extensions that include gene expression is a powerful approach for the analysis of complex biochemical networks (1-4). In MCA, the control exerted by an enzyme on a concentration of any substance X (5) is quantified by its concentration control coefficient, which is defined as the percentage increase of the steady-state concentration of X that results from a 1% activation of the enzyme of interest. The sum of the concentration control coefficients of all the enzymes in the network is 0. This reflects that (i) activation of some enzymes increases the concentration of X, whereas activation of other enzymes should reduce the concentration of X (these enzymes have negative concentration control coefficients), and (ii) the positive controls together are equal to the negative controls. The principles of MCA do not only apply to metabolic pathways; they can also be used and extended to dissect the control distribution in regulatory pathways beyond steady state (for example see Refs.6 and 7) or gene expression cascades (for example see e.g. Ref. 8). Earlier MCA, as also applied to trypanosomes, has looked more at the control of fluxes, showing that usually flux control coefficients are smaller than 1, because several enzymes partially...

show abstract

“…T. brucei has three PGK genes (3,4). One, PGKA, encodes a minor glycosomal variant (PGKA) that is expressed at low levels in both bloodstream and procyclic forms (5,6). The second gene, PGKB, encodes the major cytosolic enzyme PGKB, which is present only in procyclic forms.…”

mentioning

confidence: 99%

Compartmentation of phosphoglycerate kinase in Trypanosoma brucei plays a critical role in parasite energy metabolism

Blattner

Helfert

Michels

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

African trypanosomes compartmentalize glycolysis in a microbody, the glycosome. When growing in the mammalian bloodstream, trypanosomes contain only a rudimentary mitochondrion, and the first seven glycolytic enzymes, including phosphoglycerate kinase, are located in the glycosome. Procyclic trypanosomes, growing in the gut of tsetse f lies, possess a fully developed mitochondrion that is active in oxidative phosphorylation. The first six glycolytic enzymes are still glycosomal, but phosphoglycerate kinase is now found in the cytosol. We demonstrate here that bloodstream trypanosomes are killed by expression of cytosolic phosphoglycerate kinase. The toxicity depends on both enzyme activity and cytosolic location. One possible explanation is that cytosolic phosphoglycerate kinase creates an ATPgenerating shunt in the cytosol, thus preventing full ATP regeneration in the glycosome and ultimately inhibiting the first, ATP-consuming, steps of glycolysis.All members of the order Kinetoplastida contain microbodies harboring glycolytic enzymes (1). Some enzymes are exclusive to the glycosome, whereas others are present in both glycosome and cytosol. In addition, the compartmentalization is developmentally regulated to varying degrees depending on the species. Kinetoplastid metabolism is simplest in the African trypanosome Trypanosoma brucei (2). T. brucei multiplies extracellularly as ''bloodstream forms'' in the blood and tissue fluids of mammals, and as ''procyclic forms'' in the gut of the tsetse fly vector. The bloodstream forms possess only a rudimentary mitochondrion and survive exclusively by substratelevel phosphorylation, with glucose-abundantly available in the environment-as the only energy source. In tsetse flies, in which amino acids are the predominant substrate; the mitochondrion is well developed, with citric acid cycle enzymes and a respiratory chain (2).One of the many enzymatic differences between bloodstream and procyclic forms is the location of phosphoglycerate kinase (PGK). T. brucei has three PGK genes (3, 4). One, PGKA, encodes a minor glycosomal variant (PGKA) that is expressed at low levels in both bloodstream and procyclic forms (5, 6). The second gene, PGKB, encodes the major cytosolic enzyme PGKB, which is present only in procyclic forms. The third gene, PGKC, encodes the major glycosomal enzyme PGKC, expressed only in bloodstream forms (3). PGKC is directed to the glycosome by a signal sequence present at the end of a 20-amino acid C-terminal extension (7-9). The developmental regulation of PGKB and PGKC expression is mediated posttranscriptionally by sequences in the 3Ј untranslated regions of the mRNAs (10). Here we describe experiments showing that correct developmentally regulated compartmentalization of PGK is vital for bloodstream trypanosome survival. MATERIALS AND METHODSPlasmid Constructs. Plasmids for inducible expression of PGK genes were constructed by replacing the chloramphenicol acetyltransferase or luciferase cassettes in pHD 615, pHD 616, or pHD 451 (11) with the ...

show abstract

Characterization of a divergent glycosomal microbody phosphoglycerate kinase from Trypanosoma brucei

Cited by 29 publications

References 19 publications

Protein trafficking in kinetoplastid protozoa.

Protein trafficking in kinetoplastid protozoa.

Control and Regulation of Gene Expression

Compartmentation of phosphoglycerate kinase in Trypanosoma brucei plays a critical role in parasite energy metabolism

Contact Info

Product

Resources

About