Posts tagged sodium pump
Articles and news from the latest research reports.
Researchers Reveal a New Pathway Through the Sodium Pump
A study in The Journal of General Physiology provides new evidence that the ubiquitous sodium pump is more complex—and more versatile—than we thought.
(Image caption: Structure of the sodium pump, which researchers reveal to be more versatile than previously thought)
The sodium pump is present in the surface membrane of all animal cells, using energy derived from ATP to transport sodium and potassium ions in opposite directions across the cell boundary. By setting up transmembrane gradients of these two ions, the pump plays a vital role in many important processes, including nerve impulses, heartbeats, and muscular contraction.
Now, Rockefeller University researchers Natascia Vedovato and David Gadsby demonstrate that, in addition to its role as a sodium and potassium ion transporter, the pump can simultaneously import protons into the cell. Their study not only provides evidence of “hybrid” function by the pump, it also raises important questions about whether the inflow of protons through sodium pumps might play a role in certain pathologies.
The sodium pump exports three sodium ions out of the cell and imports two potassium ions into the cell during each transport cycle. Vedovato and Gadsby show that, during this normal cycle, the pump develops a passageway that enables protons to cross the membrane. When the pump releases the first of the three sodium ions to the cell exterior, a newly emptied binding site becomes available for use by an external proton, allowing it to then make its way into the cytoplasm. The protons travel a distinct route, and proton inflow is not required for successful transport of sodium and potassium.
Import of protons is high when their extracellular concentration is high (pH is low) and membrane potential is negative. The authors therefore speculate that proton inflow might have important implications under conditions in which extracellular pH is lowered, such as in muscle during heavy exercise, in the heart during a heart attack, or in the brain during a stroke.
(Source: newswise.com)
Mechanism of hearing is similar to car battery
University of Iowa biologist Daniel Eberl and his colleagues have shown that one of the mechanisms involved in hearing is similar to the battery in your car.
And if that isn’t interesting enough, the UI scientists advanced their knowledge of human hearing by studying a similar auditory system in fruit flies—and by making use of the fruit fly “love song.”
To see how the mechanism of hearing resembles a battery, you need to know that the auditory system of the fruit fly contains a protein that functions as a sodium/potassium pump, often called the sodium pump for short, and is highly expressed in a specialized support cell called the scolopale cell.
The scolopale cell is important because it wraps around the sensory endings in the fly’s ear and makes a tight extra-cellular cavity or compartment around them called the scolopale space.
“You could think of these compartments as similar to the compartments of a battery that need to be charged up so they can drive electrons through circuits,” says Eberl, whose paper made the cover of the journal Proceedings of the National Academy of Sciences. “In the auditory system, the charge in the scolopale space drives ions, or electrically charged atoms, through membrane channels in the sensory endings that open briefly in response to activation by sounds.
“Our work shows that the sodium pump plays a particularly important role in this cell to help replenish or recharge this compartment with the right ions. The human ear also relies on a compartment called the scala media, which similarly drives ions into the sensory cells of the ear,” he says.
How was the research done? This is where the fruit fly love song comes into play.
Testing whether or not a fruit fly can hear the love song—a sound generated by a vibrating wing—enables Eberl to learn whether electrical recharging is occurring in the fly ear. The fruit fly love song played a role in the research by stimulating the fly to move whenever a sound was emitted and received.
“In these experiments we tested the fly’s hearing by inserting tiny electrodes in the fly’s antenna, then measuring the electrical responses when we play back computer-generated love songs,” he says.
Eberl notes there are many similarities between fruit fly and human mechanisms of hearing. That means his work on the fly model to identify additional new components required for generating the correct ion balance in the ear will help scientists to understand the human process in more detail.