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Proteins and lipids of glycosomal membranes from Leishmania tarentolae and Trypanosoma brucei

Colasante, Claudia; Voncken, Frank; Manful, Theresa; Ruppert, Thomas; Tielens, Aloysius G M; van Hellemond, Jaap J; Clayton, Christine

Authors

Claudia Colasante

Frank Voncken F.Voncken@hull.ac.uk

Theresa Manful

Thomas Ruppert

Aloysius G M Tielens

Jaap J van Hellemond

Christine Clayton



Abstract

In kinetoplastid protists, several metabolic pathways, including glycolysis and purine salvage, are located in glycosomes, which are microbodies that are evolutionarily related to peroxisomes. With the exception of some potential transporters for fatty acids, and one member of the mitochondrial carrier protein family, proteins that transport metabolites across the glycosomal membrane have yet to be identified. We show here that the phosphatidylcholine species composition of membranes resembles that of other cellular membranes, which means that glycosomal membranes are expected to be impermeable to small hydrophilic molecules unless transport is facilitated by specialized membrane proteins. Further, we identified 464 proteins in a glycosomal membrane preparation from Leishmania tarentolae. The proteins included approximately 40 glycosomal matrix proteins, and homologues of peroxisomal membrane proteins - PEX11, GIM5A and GIM5B; PXMP4, PEX2 and PEX16 - as well as the transporters GAT1 and GAT3. There were 27 other proteins that could not be unambiguously assigned to other compartments, and that had predicted trans-membrane domains. However, no clear candidates for transport of the major substrates and intermediates of energy metabolism were found. We suggest that, instead, these metabolites are transported via pores formed by the known glycosomal membrane proteins.

Journal Article Type Article
Publication Date Jan 29, 2013
Journal F1000Research
Publisher F1000Research
Peer Reviewed Peer Reviewed
Volume 2
Pages 0 - 0
APA6 Citation Colasante, C., Voncken, F., Manful, T., Ruppert, T., Tielens, A. G. M., van Hellemond, J. J., & Clayton, C. (2013). Proteins and lipids of glycosomal membranes from Leishmania tarentolae and Trypanosoma brucei. F1000Research, 2, 0 - 0. doi:10.3410/f1000research.2-27.v1
DOI https://doi.org/10.3410/f1000research.2-27.v1
Additional Information Referee status: Indexed; Referee Report: Ralf Erdmann Department of Biochemistry Systems, Institute of Physiological Chemistry, Ruhr-Universität Bochum, Bochum, Germany Approved: 08 February 2013 (v1); I have read this submission. I believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. ; Glycosomes are evolutionarily and functionally related to peroxisomes. To fulfill their metabolic functions, the organelles communicate with the cytosol by an exchange of metabolites/products. Driven by the fact that the knowledge on metabolite transport across the glycosomal membrane and the nature of involved protein in this process is still scarce, the authors performed a proteomic approach with purified organelles. The paper is well written, the experimental design and results are conclusive. Some minor comments should be addressed:- Figure 1A: Please indicate top/bottom fractions and provide some information of the density at least of the peak fractions. Please mention in the legend how much of the total fractions was subjected to the gel.- Figure 1B: Please indicate the load. Are the membranes enriched compared to the glycosomal fraction? Please also provide more details on the experimental approach in the methods section, like volumes used for resuspension, fractions loaded on the gel, etc.; Competing Interests: No competing interests were disclosed.; Referee Report: Peter Myler Seattle Biomedical Research Institute, Seattle, WA, USA Approved: 27 March 2013 (v1); I have read this submission. I believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. ; In this manuscript, Colasante et al. describe an exhaustive analysis of the membrane proteins and lipids present in glycosomes from the kinetoplastid protozoan parasite, Leishmania tarentolae, and conclude that, in the absence of obvious transporters for the major substrates and intermediates of energy metabolism, these molecules must be transported across the glycosomal membrane via pores formed by known glycosomal membrane proteins, which are orthologues of the peroxisomal membrane proteins PEX11, GIM5A/B, PXMP4, PEX2 and PEX16. The paper is well-written and the technical approach is appropriate. While one must be mindful of the adage “absence of evidence is not evidence of absence”, the comprehensive nature of the proteomic analysis in the present study provides a persuasive argument (albeit, not definitive proof) for this conclusion. As a minor point, it could perhaps have been helpful to have indicated the identity of the proteins enriched in the glycosomal membrane fraction (urea pellet) of Table 1B. It would also be good to indicate what proportions of the total glycosomal fraction are represented by the two lanes in this figure.; Competing Interests: No competing interests were disclosed.
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