Work in our laboratory is directed toward the exploration of the cell biology, physiology, biochemistry, and host-parasite interactions of several parasites of humans of major public health importance. The parasites are studied at the cellular and molecular levels with a combination of biochemical, molecular biological, and morphological tools. The problems explored are largely basic with significant potential for contributing to the understanding of pathogenesis of parasitic diseases and to the development of new preventive or curative agents.
Research in our laboratory is devoted to a comparative exploration of the main types of energy metabolism and its organelles in parasitic anaerobic protists. These include pathogens of humans, Trichomonas vaginalis causing vaginitis, and Entamoeba histolytica and Giardia lamblia, which cause intestinal diseases. These protists are representatives of several unrelated branches of the eukaryotic phylogenetic tree. They differ fundamentally from most eukaryotic organisms in lacking mitochondria. Their glucose catabolism is characterized by several distinguishing features. (a) Regulation of glycolysis is unusual. (b) Pyruvate oxidation is dependent on an enzyme, pyruvate:ferredoxin oxidoreductase, which is highly different from the isofunctional pyruvate dehydrogenase complex in aerobic eukaryotes. (c) In some organisms instead of mitochondria, hydrogenosomes are present in which pyruvate or malate oxidation leads to production of H2. These organelles, discovered in our laboratory, are still incompletely known. We are working on elucidating the origin of similar metabolic patterns and of the presence of hydrogenosomes in diverse organisms. Our studies are performed partly through a comparison of the primary structure and functional properties of key proteins of these organisms with each other and with related proteins of other organisms and partly by functional and biochemical studies on whole cells and their hydrogenosomes.
Hrd«y, I., and M. Müller. 1995. Primary structure and eubacterial relationships of the pyruvate:ferredoxin oxidoreductase of the amitochondriate eukaryote, Trichomonas vaginalis. Journal of Molecular Evolution. In press.
LŠnge, S., C. Rozario, and M. Müller. 1994. Primary structure of the hydrogenosomal adenylate kinase of Trichomonas vaginalis and its phylogenetic relationships. Molecular and Biochemical Parasitology. 66:297-308.
Markos, A., A. Miretsky, and M. Müller. 1993. A glyceraldehyde 3-phosphate dehydrogenase with eubacterial features in the amitochondriate eukaryote, Trichomonas vaginalis. Journal of Molecular Evolution. 37:631-643.
Mertens, E., E. Van Schaftingen, and M. Müller. 1992. Pyruvate kinase from Trichomonas vaginalis, an allosteric enzyme stimulated by ribose 5-phosphate and glycerate 3-phosphate. Molecular and Biochemical Parasitology. 54:13-20.
Müller, M. 1992. Energy metabolism of ancestral eukaryotes: a hypothesis based on the biochemistry of amitochondriate parasitic protists. BioSystems. 28:33-40.
Müller, M. 1993. The hydrogenosome. Journal of General Microbiology. 139:2879-2889.
Rozario, C., M.W. Smith, and M. Müller. 1995. Primary sequence of a putative pyrophosphate-linked phosphofructokinase gene of Giardia lamblia. Biochimica et Biophysica Acta. 1260:218-222.
Ter Kuile, B.H., and M. Müller, 1993. Interaction between facilitated diffusion of glucose across the plasma membrane and its metabolism in Trichomonas vaginalis. FEMS (Federation of European Microbiological Societies) Microbiology Letters. 110:27-32.
Ter Kuile, B.H., and M. Müller. 1995. Maltose utilization by extracellular hydrolysis followed by glucose transport in Trichomonas vaginalis. Parasitology. 110:37-44.
My research concentrates on understanding intracellular interactions using energy metabolism in the parasitic protists Trypanosoma brucei, Leishmania donovani, and Trichomonas vaginalis as models. The aim is to describe how cellular processes, such as transport, enzymatic reactions, and energy generation are adjusted to each other in the living cell. These eukaryotic organisms have a relatively simple metabolism. All three species adapt their glucose uptake and metabolic rates to substrate availability and growth rate, but in different ways. By changing the growth conditions in a strictly controlled manner in the chemostat it has been possible to analyze the way organisms adapt, thereby elucidating their metabolic strategies. In T. brucei the activities of the glucose transporter in the plasma membrane and those of the enzymes in the subsequent metabolic pathway are finely adjusted to each other, with minimum overcapacity of each individual step. In L. donovani adaptation is minimal, but T. vaginalis adapts in a manner that counteracts the changes in growth conditions. This confirms earlier suggestions by others that energy metabolism is organized to provide functional homeostasis at minimal energy expense. The emphasis of these metabolic adjustments depends on the ecology of the organism. In a constant environment it is aimed at achieving maximum energy efficiency, in challenging and rapidly changing environments at maintaining internal homeostasis. By linking different types of information we attempt to provide a detailed insight into the organization of carbon and energy metabolism at the cellular, enzymatic and molecular level.
Ter Kuile, B. H. 1993. Glucose and proline transport in Kinetoplastids, protozoan parasites. Parasitology Today. 9:206-210.
Ter Kuile, B. H. 1994a. Adaptation of the carbon metabolism of Trichomonas vaginalis to the nature and availability of the carbon source. Microbiology. 140:2503-2510.
Ter Kuile, B. H. 1994b. Carbohydrate metabolism and physiology of the parasitic protist Trichomonas vaginalis studied in chemostats. Microbiology. 140:2495-2502.
Ter Kuile, B. H. 1994c. Membrane related processes and overall energy metabolism in Trypanosoma brucei and other kinetoplastid species. Journal of Bioenergetics and Biomembranes. 26:167-172.
Ter Kuile, B. H., and M. Cook. 1994. The kinetics of facilitated diffusion followed by enzymatic conversion of the substrate. Biochimica et Biophysica Acta. 1193:235-239.
Ter Kuile, B. H., and M. Müller. 1995. Maltose utilization by extracellular hydrolysis followed by glucose transport in the amitochondriate eukaryote, Trichomonas vaginalis. Parasitology. 110:37-44.
Miklós Müller
Professor
Christian de Duve
Benno ter Kuile
Leena Nevalainen-Smith
Lidya Sanchez