A Human Transporter Protein that Mediates the Final Excretion Step for

Introduction The kidney is an excretory organ that filters wastes from blood and excretes them as urine. Blood plasma filtration occurs at the glomerulus, which is a network of capillaries. Transporters are specialized proteins located in the membranes of the nephron. There are different concentrations of transporters located at various regions of the nephron. For instance, the proximal tubule retains most of the sodium transporters. Some transporters require adenosine triphosphate while others perform passive transport. The method of excretion of toxic organic compounds in mammals is mainly through the kidney and liver. Toxic organic compounds are absorbed by the basolateral membranes and later excreted by brush border membranes that absorb nutrients from the small intestine. These toxic organic compounds are also absorbed by hepatocytes at the sinusoidal membranes and excreted through the bile canaliculi. The objective of this research is to identify the transporter involved with the final step of excretion of toxic organic chemicals. Based on biochemical and physiological studies of the organic compound exporter, the tentative hypothesis proposed is that mammalian orthologues of bacterial multidrug are involved with the excretion of organic compounds. These multidrug transporters include the ?major facilitator superfamily, the small multidrug resistance family, the resistance nodulation cell division family, the ATP binding cassette family, and the multidrug and toxin extrusion (M ATE) family (8?10)?. The MATE family proteins facilitate the coupled export between hydrogen and sodium ions of cationic drugs in bacteria. In this experiment, MATE1 is revealed as the transporter involved with the final... ... locations fit the description of a H+ coupled organic cation transporter. Does hMATE have the correct physiological fingerprint for a toxic organic cation exporter? Yes! Even before they discovered this protein transporter, physiologists had a set of characteristics that this unknown transport protein would display. This protein would be pH sensitive, use H+ as the active step in secondary active transport, and saturable of course. In addition, this protein is found just where it should be, in the apical regions of tubes in the kidney and liver. Since hMATE fits the description, it is a convincing suspect for exporting toxic organic cations. Sources Article: A human transporter protein that mediates the final excretion step for toxic organic cations. By: Masato Otsuka, Takuya Matsumoto, Riyo Morimoto, Shigeo Arioka, Hiroshi Omote, and Yoshinori Moriyama