Co-transport

Co-transport, also known as coupled transport or secondary active transport, refers to the simultaneous or sequential passive transfer of molecules or ions across biological membranes in a fixed ratio. Permitting one ion or molecule to move from the side where it is more concentrated to that where it is less concentrated increases entropy and can serve as a source of energy for metabolism (e.g. in ATP synthase). In cotransporters, it is used to force the transport of another ion or molecule (usually) from the side where it is less concentrated to that where it is more concentrated. Cotransporters can be classified as symporters and antiporters depending on whether the substances move in the same or opposite directions .

Discovery of cotransport

In August 1960, in Prague, Robert K. Crane presented for the first time his discovery of the sodium-glucose cotransport as the mechanism for intestinal glucose absorption.^[1] Crane's discovery of cotransport was the first ever proposal of flux coupling in biology. ^[2][3]

See also

• Cotransporter
• Symporter
• Sodium/phosphate cotransporter
• Sodium-glucose transport proteins
• Glucose transporter

References

1. ^ Robert K. Crane, D. Miller and I. Bihler. “The restrictions on possible mechanisms of intestinal transport of sugars”. In: Membrane Transport and Metabolism. Proceedings of a Symposium held in Prague, August 22–27, 1960. Edited by A. Kleinzeller and A. Kotyk. Czech Academy of Sciences, Prague, 1961, pp. 439-449.
2. ^ Ernest M. Wright and Eric Turk. “The sodium glucose cotransport family SLC5”. Pflügers Arch 447, 2004, p. 510. “Crane in 1961 was the first to formulate the cotransport concept to explain active transport [7]. Specifically, he proposed that the accumulation of glucose in the intestinal epithelium across the brush border membrane was coupled to downhill Na+ transport cross the brush border. This hypothesis was rapidly tested, refined and extended [to] encompass the active transport of a diverse range of molecules and ions into virtually every cell type.”
3. ^ Boyd, C A R. “Facts, fantasies and fun in epithelial physiology”. Experimental Physiology, Vol. 93, Issue 3, 2008, p. 304. “the insight from this time that remains in all current text books is the notion of Robert Crane published originally as an appendix to a symposium paper published in 1960 (Crane et al. 1960). The key point here was 'flux coupling', the cotransport of sodium and glucose in the apical membrane of the small intestinal epithelial cell. Half a century later this idea has turned into one of the most studied of all transporter proteins (SGLT1), the sodium–glucose cotransporter.. ”

• "Cotransport by Symporters and Antiporters". http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowSection&rid=mcb.section.4098.