Featured Research

from universities, journals, and other organizations

Rhesus proteins transport ions, not gas

Date:
June 27, 2014
Source:
Albert-Ludwigs-Universität Freiburg
Summary:
Membrane proteins: do they carry the gas ammonia or the ammonium ion in their luggage? And is transport active or passive? Biochemists have long speculated on the mechanistic details of the ammonium transport family of proteins (Amt), which include the Rhesus protein factors, known as the mammalian blood group system. In mammals, Rhesus proteins regulate acid and ion balance in kidney and liver cells. New research sheds new light on this issue.

Proteins of the Amt family transport ammonium across the lipid membrane of the cell.
Credit: Susana Andrade

Do they carry the gas ammonia or the ammonium ion in their luggage? And is transport active or passive? Biochemists have long speculate on the mechanistic details of the ammonium transport family of proteins (Amt), which include the Rhesus protein factors, known as the mammalian blood group system. What was previously known is that Amt proteins extend across cellular membranes where they specifically transport the nitrogen into bacteria and plant cells, essential nutrient for their growth and survival. In mammals, Rhesus proteins regulate acid and ion balance in kidney and liver cells. A team of scientists led by Prof. Dr. Susana Andrade from the Institute of Biochemistry of the University of Freiburg and the Cluster of Excellence BIOSS Centre for Biological Signalling Studies has now determined the transport properties of Amt proteins with great precision on the basis of electrophysiology tests on artificial lipid systems.

The scientists cloned the membrane proteins from an archaea, a microorganisms that lives under extreme temperature conditions and isolate them. In 2005, the Freiburg researchers already threw light on the crystalline three-dimensional structure of a protein of this kind. Now they have added the protein to a layer of lipid molecules, enabling them to measure the ion currents directly. The team discovered that a positive charge travels through the membrane: The membrane proteins do not transport the gas ammonia NH3 but rather the ammonium ion NH4+. The researchers published their findings in the journal Proceedings of the National Academy of Sciences of the USA.

"The results can, in a large part, be transferred to the Rhesus proteins from mammals," says Andrade as Amt proteins bear a close resemblance to the Rhesus proteins found in humans. They are produced in the blood, in the kidney, and in the liver, where they regulate the intake of ammonium and thus the body's pH. The researchers tested three Amt proteins that are present in the bacteria and also determined the speed with which they allow ammonium to pass through the membrane. "In the future, we want to modify individual components of the transporter to improve our understanding of the exact molecular details involved" explains Andrade.

The scientific debate on Amt/Rh proteins stems from the difficulty of distinguishing between ammonia and ammonium in measurements, as the two molecules are transformed into each other in a continuous state of balance with protons. "Our in vitro method gives us a level of precision that finally allows us to draw valid conclusions concerning the transport process," stresses the researcher.


Story Source:

The above story is based on materials provided by Albert-Ludwigs-Universität Freiburg. Note: Materials may be edited for content and length.


Journal Reference:

  1. T. Wacker, J. J. Garcia-Celma, P. Lewe, S. L. A. Andrade. Direct observation of electrogenic NH4 transport in ammonium transport (Amt) proteins. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1406409111

Cite This Page:

Albert-Ludwigs-Universität Freiburg. "Rhesus proteins transport ions, not gas." ScienceDaily. ScienceDaily, 27 June 2014. <www.sciencedaily.com/releases/2014/06/140627094555.htm>.
Albert-Ludwigs-Universität Freiburg. (2014, June 27). Rhesus proteins transport ions, not gas. ScienceDaily. Retrieved September 23, 2014 from www.sciencedaily.com/releases/2014/06/140627094555.htm
Albert-Ludwigs-Universität Freiburg. "Rhesus proteins transport ions, not gas." ScienceDaily. www.sciencedaily.com/releases/2014/06/140627094555.htm (accessed September 23, 2014).

Share This



More Plants & Animals News

Tuesday, September 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Ice Age Wooly Mammoth Remains for Sale

Raw: Ice Age Wooly Mammoth Remains for Sale

AP (Sep. 23, 2014) — A rare, well-preserved skeleton of a woolly mammoth is going on sale at Summers Place Auctions hope the 11.5-foot tall, almost intact specimen will fetch between $245,000 to $409,000. (Sept. 23) Video provided by AP
Powered by NewsLook.com
Fox Bites Conn. Student And School Staffers In Rare Attack

Fox Bites Conn. Student And School Staffers In Rare Attack

Newsy (Sep. 23, 2014) — A fox attacked a second-grade boy at a Connecticut elementary school Monday. It also attacked two school staff members and a woman and her dog. Video provided by Newsy
Powered by NewsLook.com
Will Living Glue Be A Thing?

Will Living Glue Be A Thing?

Newsy (Sep. 23, 2014) — Using proteins derived from mussels, engineers at MIT have made a supersticky underwater adhesive. They're now looking to make "living glue." Video provided by Newsy
Powered by NewsLook.com
Raw: Tiger Kills Man at India Zoo

Raw: Tiger Kills Man at India Zoo

AP (Sep. 23, 2014) — A white tiger killed a young man who climbed over a fence at the New Delhi zoo and jumped into the animal's enclosure on Tuesday, a spokesman said. (Sept. 23) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins