Fundamentals

What are ion channels?

BY      |     January 10, 2020

“…Definitions overlap but they almost never coincide.” Russell Lynes

We all think differently and use different words/associations to describe the same thing. Here I gathered various definitions of ion channels I could find for you. Enjoy!

1791 – Luigi Galvani suspected the existence of water-filled holes allowing the current flow through the surface of muscle and nerve fibers.

1955 – Alan Hodgkin and Richard Keynes were first to use the word “channel” to describe the possible way by which K+ ions cross the membrane. “…ions cross the membrane through narrow tubes or channels…in which the ions are constrained to move in single file” (Hodgkin&Keyness, J.Physiol., 1955).

1960s-1970s – Clay Armstrong, Bertil Hille and Francisco Bezanilla introduced and developed the concept of ion channels as macromolecular aqueous pores made of protein. They also coined such a widely used terms as selectivity filter, voltage sensor, gating, inner and outer vestibules, and gating current.

Ion channels are macromolecular pores in cell membranes. (Bertil Hille, Ion channels of excitable membranes, 2001)

Ionic channels are gated aqueous pores whose conformational changes are driven by the electric field in the membrane. (Bertil Hille, Biophys J. 1978)

Ion channels are molecular transducers that switch on and off electrical currents that are carried by ions across biological membranes. (Frederick Sigworth, The Sigworth Laboratory website)

Ion channels are passive conduits for ions to cross the membrane. (Roderick MacKinnon, NIH Director’s Wednesday Afternoon Lecture Series, 2017)

Ion channels are a major class of membrane signaling proteins that produce changes in transmembrane electrical potential in response to many different stimuli… Activation of the ion channels opens a selective transmembrane pore through which specific ions may diffuse down their electrochemical gradient into or out of the cell. (William A. Catteral, J Bioenerg Biomembr. 1996)

Ion channels are membrane proteins that act as gated pathways for the movement of ions across cell membranes. (Frances Ashcroft, Ion Channels and Disease, 1999)

Ion channels are transmembrane proteins that form rapidly activating and inactivating pores that permit ions to flow down their electrochemical gradients and across cell membranes. (Daniel L Minor, An Overview of Ion Channel Structure, 2010)

Ion channels are macromolecular protein tunnels that span the lipid bilayer of the cell membrane. (Ackerman&Clapham, N Engl J Med. 1997)

Ion channel, protein expressed by virtually all living cells that creates a pathway for charged ions from dissolved salts, including sodium, potassium, calcium, and chloride ions, to pass through the otherwise impermeant lipid cell membrane. (James Huettner, Encyclopedia Britannica)

Ion channels facilitate the movement of ions across the plasma and organellar membranes. (Feske S., Sci Signal. 2019)

Ion channels are proteins that essentially form holes, or “pores,” in the membrane, allowing selected ions to pass through. (Bockenhauer D., Curr Opin Pediatr. 2001)

Ion channels are integral membrane proteins that form a pore to allow the passage of specific ions by passive diffusion. (Jentsch TJ et al., Nat Cell Biol. 2004)

Ion channels are integral membrane proteins that contain pathways through which ions can flow. (Di Resta C., Adv Exp Med Biol. 2010)

Ion channels are specialized transmembrane proteins that permit the passive flow of ions following their electrochemical gradients. (Valverde MA, J Biol Chem. 2011)

Ion channels are membrane-bound enzymes whose catalytic sites are ion-conducting pores that open and close (gate) in response to specific environmental stimuli. (Sigg D., J Gen Physiol. 2014)

Ion channels are complex polytopic transmembrane proteins that control the transfer of ions across biological membranes via a gated pore. (Wilkinson TC et al., J Biomol Screen. 2015)

Ion channels provide energetically favorable passage for ions to diffuse rapidly and passively according to their electrochemical potential. (Roux B., Essays Biochem. 2017)

Ion channels are pore-forming transmembrane proteins that allow the regulated flow of cations or anions across membranes. (Wulff H., Nat Rev Drug Discov. 2019)

Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. (Wikipedia)

Ion channels are integral membrane proteins that allow the passive passage of certain ions into and out of the cell. (Prevarskaya et al., Trends Mol Med. 2010)

Ion channels are integral pore-forming membrane proteins that mediate passive influx/efflux of essential signaling ions into/from the cell or intracellular organelles thereby controlling cytoplasmic/intraorganellar ion concentrations. (Kondratskyi et al. Autophagy, 2017)

Ion channels are pore-forming transmembrane proteins that allow the regulated flow of cations or anions across membranes. (Wulff H., Nat Rev Drug Discov. 2019)

Ion channels are protein molecules that span across the cell membrane allowing the passage of ions from one side of the membrane to the other. (Barker et al., Conn’s Translational Neuroscience, 2017)

Ion channels are integral membrane protein assemblies that modulate the flow of ions into and out of a cell or organelle, leading to generation of electrical signals. (Nature.com)

If you have your own way of saying what ion channels are, I would love to hear from you.


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