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Kinetoplastid PPEF phosphatases: dual acylated proteins expressed in the endomembrane system of Leishmania.

ABSTRACT: Bioinformatic analyses have been used to identify potential downstream targets of the essential enzyme N-myristoyl transferase in the TriTryp species, Leishmania major, Trypanosoma brucei and Trypanosoma cruzi. These database searches predict approximately 60 putative N-myristoylated proteins with high confidence, including both previously characterised and novel molecules. One of the latter is an N-myristoylated protein phosphatase which has high sequence similarity to the Protein Phosphatase with EF-Hand (PPEF) proteins identified in sensory cells of higher eukaryotes. In L. major and T. brucei, the PPEF-like phosphatases are encoded by single-copy genes and are constitutively expressed in all parasite life cycle stages. The N-terminus of LmPPEF is a substrate for N-myristoyl transferase and is also palmitoylated in vivo. The wild type protein has been localised to the endocytic system by immunofluorescence. The catalytic and fused C-terminal domains of the kinetoplastid and other eukaryotic PPEFs share high sequence similarity, but unlike their higher eukaryotic relatives, the C-terminal parasite EF-hand domains are degenerate and do not bind calcium.

SUBMITTER: Mills E

PROVIDER: S-EPMC1885993 | biostudies-literature | 2007 Mar

REPOSITORIES: biostudies-literature

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Kinetoplastid PPEF phosphatases: dual acylated proteins expressed in the endomembrane system of Leishmania.

Mills Elena E Price Helen P HP Johner Andrea A Emerson Jenny E JE Smith Deborah F DF

Molecular and biochemical parasitology 20061204 1

Bioinformatic analyses have been used to identify potential downstream targets of the essential enzyme N-myristoyl transferase in the TriTryp species, Leishmania major, Trypanosoma brucei and Trypanosoma cruzi. These database searches predict approximately 60 putative N-myristoylated proteins with high confidence, including both previously characterised and novel molecules. One of the latter is an N-myristoylated protein phosphatase which has high sequence similarity to the Protein Phosphatase w ...[more]

PMID: 17169445

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Project description:BackgroundThe discovery of the autotransporter family has provided a mechanism for surface expression of proteins in laboratory strains of Escherichia coli. We have previously reported the use of the AIDA-I autotransport system to express the Salmonella enterica serovar Enteritidis proteins SefA and H:gm. The SefA protein was successfully exposed to the medium, but the orientation of H:gm in the outer membrane could not be determined due to proteolytic cleavage of the N-terminal detection-tag. The goal of the present work was therefore to construct a vector containing elements that facilitates analysis of surface expression, especially for proteins that are sensitive to proteolysis or otherwise difficult to express.ResultsThe surface expression system pAIDA1 was created with two detection tags flanking the passenger protein. Successful expression of SefA and H:gm on the surface of E. coli was confirmed with fluorescently labeled antibodies specific for the N-terminal His6-tag and the C-terminal Myc-tag. While both tags were detected during SefA expression, only the Myc-tag could be detected for H:gm. The negative signal indicates a proteolytic cleavage of this protein that removes the His6-tag facing the medium.ConclusionsExpression levels from pAIDA1 were comparable to or higher than those achieved with the formerly used vector. The presence of the Myc- but not of the His6-tag on the cell surface during H:gm expression allowed us to confirm the hypothesis that this fusion protein was present on the surface and oriented towards the cell exterior. Western blot analysis revealed degradation products of the same molecular weight for SefA and H:gm. The size of these fragments suggests that both fusion proteins have been cleaved at a specific site close to the C-terminal end of the passenger. This proteolysis was concluded to take place either in the outer membrane or in the periplasm. Since H:gm was cleaved to a much greater extent then the three times smaller SefA, it is proposed that the longer translocation time for the larger H:gm makes it more susceptible to proteolysis.

Project description:Protein-coding genes in kinetoplastid protists are transcribed from polycistronic arrays, yielding RNA precursors which are processed to form mature transcripts bearing a 5M-bM-^@M-^Y spliced leader (SL) and 3M-bM-^@M-^Y poly(A) tract. Regions of transcription initiation and termination lack known eukaryotic promoter and terminator elements, and current data suggest that transcription is instead regulated predominantly through epigenetic mechanisms. Several epigenetic marks, including histone modifications, histone variants, and an atypical DNA modification known as base J have been localized to regions of transcription initiation or termination in Trypanosoma brucei, Trypanosoma cruzi, and/or Leishmania major. Despite this conservation, the phenotypes of base J mutants vary significantly across trypanosomatids, suggesting that the specific epigenetic networks governing transcription initiation and termination have diverged significantly during evolution. In this light, we sought to characterize and compare the roles of the histone variants H2A.Z, H2B.V, and H3.V in L. major. As in T. brucei, the histone variants H2A.Z and H2B.V were shown to be essential in L. major using a powerful quantitative plasmid segregation-based test. In contrast and again similar to T. brucei, H3.V is not essential in Leishmania as H3.V-null lines grew normally, resembled WT, and remained infectious. Using SL-primed RNA-seq, we found that H3.V-null parasites have steady-state transcript levels comparable to WT parasites and display no defects in the efficiency of transcription termination at convergent strand switch regions (SSRs). Our results show a conservation of histone variant phenotypes between L. major and T. brucei, in contrast to the phenotypes associated with the epigenetic DNA base J modification. Total RNA from Four LmjF samples were analyzed using RNA-Seq. One of them is wildtype parasites, one is single knockout for H3V gene and two independent double knockouts for H3V gene.

Project description:BackgroundLeptomonas is monogenetic kinetoplastid parasite of insects and is primitive in comparison to Leishmania. Comparative studies of these two kinetoplastid may share light on the evolutionary transition to dixenous parasitism in Leishmania. In order to adapt and survive within two hosts, Leishmania species must have acquired virulence factors in addition to mechanisms that mediate susceptibility/resistance to infection in the pathology associated with disease. Rab proteins are key mediators of vesicle transport and contribute greatly to the evolution of complexity of membrane transport system. In this study we used our whole genome sequence data of these two divergent kinetoplastids to analyze the orthologues/paralogues of Rab proteins.ResultsDuring change of lifestyle from monogenetic (Leptomonas) to digenetic (Leishmania), we found that the prenyl machinery remained unchanged. Geranylgeranyl transferase-I (GGTase-I) was absent in both Leishmania and its sister Leptomonas. Farnesyltransferase (FTase) and geranylgeranyl transferase-II (GGTase-II) were identified for protein prenylation. We predict that activity of the missing alpha-subunit (α-subunit) of GGTase-II in Leptomonas was probably contributed by the α-subunit of FTase, while beta-subunit (β-subunit) of GGTase-II was conserved and indicated functional conservation in the evolution of these two kinetoplastids. Therefore the β-subunit emerges as an excellent target for compounds inhibiting parasite activity in clinical cases of co-infections. We also confirmed that during the evolution to digenetic life style in Leishmania, the parasite acquired capabilities to evade drug action and maintain parasite virulence in the host with the incorporation of short-chain dehydrogenase/reductase (SDR/MDR) superfamily in Rab genes.ConclusionOur study based on whole genome sequences is the first to build comparative evolutionary analysis and identification of prenylation proteins in Leishmania and its sister Leptomonas. The information presented in our present work has importance for drug design targeted to kill L. donovani in humans but not affect the human form of the prenylation enzymes.

Dataset Information

Kinetoplastid PPEF phosphatases: dual acylated proteins expressed in the endomembrane system of Leishmania.

Publications

Kinetoplastid PPEF phosphatases: dual acylated proteins expressed in the endomembrane system of Leishmania.

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