Cotransport: Coupled Transport by a Membrane Protein (Campbell Biology)
A solute that exists in different concentrations across a membrane can do work as it moves across that membrane by diffusion down its concentration gradient. This is analogous to water that has been pumped uphill and performs work as it flows back down. In a mechanism called cotransport, a transport protein (a cotransporter) can couple the “downhill” diffusion of the solute to the “uphill” transport of a second substance against its own concentration gradient. For instance, a plant cell uses the gradient of H+ generated by its ATP-powered proton pumps to drive the active transport of amino acids, sugars, and several other nutrients into the cell. A cotransporter couples the return of H+ to the transport of sucrose into the cell. This protein can translocate sucrose into the cell against its concentration gradient, but only if the sucrose molecule travels in the company of an H+. The H+ uses the transport protein as an avenue to diffuse down its own electrochemical gradient, which is maintained by the proton pump. Plants use H+ /sucrose cotransport to load sucrose produced by photosynthesis into cells in the veins of leaves. The vascular tissue of the plant can then distribute the sugar to roots and other nonphotosynthetic organs that do not make their own food.
What we know about cotransport proteins in animal cells has helped us find more effective treatments for diarrhea, a serious problem in developing countries. Normally, sodium in waste is reabsorbed in the colon, maintaining constant levels in the body, but diarrhea expels waste so rapidly that reabsorption is not possible, and sodium levels fall precipitously. To treat this life-threatening condition, patients are given a solution to drink containing high concentrations of salt (NaCl) and glucose. The solutes are taken up by sodiumglucose cotransporters on the surface of intestinal cells and passed through the cells into the blood. This simple treatment has lowered infant mortality worldwide.
Urry, Lisa A.. Campbell Biology. Pearson Education. Kindle Edition. https://www.pearson.com/us/higher-education/series/Campbell-Biology-Series/2244849.html
Research Article: Auxin-Responsive DR5 Promoter Coupled with Transport Assays Suggest Separate but Linked Routes of Auxin Transport during Woody Stem Development in Populus
Date Published: August 15, 2013 Publisher: Public Library of Science Author(s): Rachel Spicer, Tracy Tisdale-Orr, Christian Talavera, Malcolm Bennett. http://doi.org/10.1371/journal.pone.0072499 Abstract: Polar auxin transport (PAT) is a major determinant of plant morphology and internal anatomy with important roles in vascular patterning, tropic growth responses, apical dominance and phyllotactic arrangement. Woody plants present a highly complex … Continue reading
Research Article: A Coupled Discrete/Continuum Model for Describing Cancer-Therapeutic Transport in the Lung
Date Published: March 12, 2012 Publisher: Public Library of Science Author(s): Karin Erbertseder, Johannes Reichold, Bernd Flemisch, Patrick Jenny, Rainer Helmig, Rongling Wu. http://doi.org/10.1371/journal.pone.0031966 Abstract: We propose a computational simulation framework for describing cancer-therapeutic transport in the lung. A discrete vascular graph model (VGM) is coupled to a double-continuum model (DCM) to determine the amount of … Continue reading
Research Article: Tachykinin-Related Peptides Share a G Protein-Coupled Receptor with Ion Transport Peptide-Like in the Silkworm Bombyx mori
Date Published: June 1, 2016 Publisher: Public Library of Science Author(s): Chiaki Nagai-Okatani, Hiromichi Nagasawa, Shinji Nagata, Erik C. Johnson. http://doi.org/10.1371/journal.pone.0156501 Abstract: Recently, we identified an orphan Bombyx mori neuropeptide G protein-coupled receptor (BNGR)-A24 as an ion transport peptide-like (ITPL) receptor. BNGR-A24 belongs to the same clade as BNGR-A32 and -A33, which were recently identified … Continue reading
Research Article: Sodium-Coupled Neutral Amino Acid Transporter 1 (SNAT1) Modulates L-Citrulline Transport and Nitric Oxide (NO) Signaling in Piglet Pulmonary Arterial Endothelial Cells
Date Published: January 15, 2014 Publisher: Public Library of Science Author(s): Anna Dikalova, Angela Fagiana, Judy L. Aschner, Michael Aschner, Marshall Summar, Candice D. Fike, Tim Lahm. http://doi.org/10.1371/journal.pone.0085730 Abstract: There is evidence that impairments in nitric oxide (NO) signaling contribute to chronic hypoxia-induced pulmonary hypertension. The L-arginine-NO precursor, L-citrulline, has been shown to ameliorate pulmonary … Continue reading
Research Article: NO3−/H+ Antiport in the Tonoplast of Cucumber Root Cells Is Stimulated by Nitrate Supply: Evidence for a Reversible Nitrate-Induced Phosphorylation of Vacuolar NO3−/H+ Antiport
Date Published: September 11, 2013 Publisher: Public Library of Science Author(s): Magdalena Migocka, Anna Warzybok, Anna Papierniak, Grażyna Kłobus, Diane Bassham. http://doi.org/10.1371/journal.pone.0073972 Abstract: Studies in the last few years have shed light on the process of nitrate accumulation within plant cells, achieving molecular identification and partial characterization of the genes and proteins involved in this … Continue reading