Skip to main content

Main menu

  • Home
  • Articles
    • Current
    • Special Feature Articles - Most Recent
    • Special Features
    • Colloquia
    • Collected Articles
    • PNAS Classics
    • List of Issues
  • Front Matter
    • Front Matter Portal
    • Journal Club
  • News
    • For the Press
    • This Week In PNAS
    • PNAS in the News
  • Podcasts
  • Authors
    • Information for Authors
    • Editorial and Journal Policies
    • Submission Procedures
    • Fees and Licenses
  • Submit
  • Submit
  • About
    • Editorial Board
    • PNAS Staff
    • FAQ
    • Accessibility Statement
    • Rights and Permissions
    • Site Map
  • Contact
  • Journal Club
  • Subscribe
    • Subscription Rates
    • Subscriptions FAQ
    • Open Access
    • Recommend PNAS to Your Librarian

User menu

  • Log in
  • My Cart

Search

  • Advanced search
Home
Home
  • Log in
  • My Cart

Advanced Search

  • Home
  • Articles
    • Current
    • Special Feature Articles - Most Recent
    • Special Features
    • Colloquia
    • Collected Articles
    • PNAS Classics
    • List of Issues
  • Front Matter
    • Front Matter Portal
    • Journal Club
  • News
    • For the Press
    • This Week In PNAS
    • PNAS in the News
  • Podcasts
  • Authors
    • Information for Authors
    • Editorial and Journal Policies
    • Submission Procedures
    • Fees and Licenses
  • Submit
Research Article

Direct observation of electrogenic NH4+ transport in ammonium transport (Amt) proteins

Tobias Wacker, Juan J. Garcia-Celma, Philipp Lewe, and Susana L. A. Andrade
  1. aInstitute for Biochemistry, Albert-Ludwigs University Freiburg, 79104 Freiburg, Germany;
  2. bDepartment of Biochemistry, University of Zürich, 8057 Zürich, Switzerland;
  3. cInstitute of Complex Systems–Cellular Biophysics Research Center Jülich, 52428 Jülich, Germany; and
  4. dBIOSS Centre for Biological Signalling Studies, 79104 Freiburg, Germany

See allHide authors and affiliations

PNAS first published June 23, 2014; https://doi.org/10.1073/pnas.1406409111
Tobias Wacker
aInstitute for Biochemistry, Albert-Ludwigs University Freiburg, 79104 Freiburg, Germany;
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Juan J. Garcia-Celma
bDepartment of Biochemistry, University of Zürich, 8057 Zürich, Switzerland;
cInstitute of Complex Systems–Cellular Biophysics Research Center Jülich, 52428 Jülich, Germany; and
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Philipp Lewe
aInstitute for Biochemistry, Albert-Ludwigs University Freiburg, 79104 Freiburg, Germany;
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Susana L. A. Andrade
aInstitute for Biochemistry, Albert-Ludwigs University Freiburg, 79104 Freiburg, Germany;
dBIOSS Centre for Biological Signalling Studies, 79104 Freiburg, Germany
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • For correspondence: andrade@bio.chemie.uni-freiburg.de
  1. Edited by H. Ronald Kaback, University of California, Los Angeles, CA, and approved June 4, 2014 (received for review April 8, 2014)

  • Article
  • Figures & SI
  • Info & Metrics
  • PDF
Loading

Significance

We have detected and analyzed electrogenic transport of ammonium and methylammonium by members of the ammonium transport (Amt) family of membrane proteins using solid-supported membrane electrophysiology. Amt transport is pH-dependent and occurs at a rate of 30–300 ions per s per trimer, well in the range of other transport proteins. The study establishes, to our knowledge, the first in vitro assay system for Amt transport in a fully controlled setup and settles debate about whether Amt proteins function as passive ammonia channels or active ammonium transporters.

Abstract

Ammonium transport (Amt) proteins form a ubiquitous family of integral membrane proteins that specifically shuttle ammonium across membranes. In prokaryotes, archaea, and plants, Amts are used as environmental NH4+ scavengers for uptake and assimilation of nitrogen. In the eukaryotic homologs, the Rhesus proteins, NH4+/NH3 transport is used instead in acid–base and pH homeostasis in kidney or NH4+/NH3 (and eventually CO2) detoxification in erythrocytes. Crystal structures and variant proteins are available, but the inherent challenges associated with the unambiguous identification of substrate and monitoring of transport events severely inhibit further progress in the field. Here we report a reliable in vitro assay that allows us to quantify the electrogenic capacity of Amt proteins. Using solid-supported membrane (SSM)-based electrophysiology, we have investigated the three Amt orthologs from the euryarchaeon Archaeoglobus fulgidus. Af-Amt1 and Af-Amt3 are electrogenic and transport the ammonium and methylammonium cation with high specificity. Transport is pH-dependent, with a steep decline at pH values of ∼5.0. Despite significant sequence homologies, functional differences between the three proteins became apparent. SSM electrophysiology provides a long-sought-after functional assay for the ubiquitous ammonium transporters.

  • ammonium transport proteins
  • Amt/Rh family
  • cation transport

Footnotes

  • ↵1To whom correspondence should be addressed. E-mail: andrade{at}bio.chemie.uni-freiburg.de.
  • Author contributions: T.W., J.J.G.-C., and S.L.A.A. designed research; T.W. and P.L. performed research; J.J.G.-C. contributed new reagents/analytic tools; T.W., J.J.G.-C., and S.L.A.A. analyzed data; and T.W., J.J.G.-C., and S.L.A.A. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1406409111/-/DCSupplemental.

Next
Back to top
Article Alerts
Email Article

Thank you for your interest in spreading the word on PNAS.

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
Direct observation of electrogenic NH4+ transport in ammonium transport (Amt) proteins
(Your Name) has sent you a message from PNAS
(Your Name) thought you would like to see the PNAS web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Citation Tools
Electrogenic Amt transport
Tobias Wacker, Juan J. Garcia-Celma, Philipp Lewe, Susana L. A. Andrade
Proceedings of the National Academy of Sciences Jun 2014, 201406409; DOI: 10.1073/pnas.1406409111

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero
Request Permissions
Share
Electrogenic Amt transport
Tobias Wacker, Juan J. Garcia-Celma, Philipp Lewe, Susana L. A. Andrade
Proceedings of the National Academy of Sciences Jun 2014, 201406409; DOI: 10.1073/pnas.1406409111
del.icio.us logo Digg logo Reddit logo Twitter logo CiteULike logo Facebook logo Google logo Mendeley logo
  • Tweet Widget
  • Facebook Like
  • Mendeley logo Mendeley
Proceedings of the National Academy of Sciences: 118 (15)
Current Issue

Submit

Sign up for Article Alerts

Jump to section

  • Article
  • Figures & SI
  • Info & Metrics
  • PDF

You May Also be Interested in

Water from a faucet fills a glass.
News Feature: How “forever chemicals” might impair the immune system
Researchers are exploring whether these ubiquitous fluorinated molecules might worsen infections or hamper vaccine effectiveness.
Image credit: Shutterstock/Dmitry Naumov.
Reflection of clouds in the still waters of Mono Lake in California.
Inner Workings: Making headway with the mysteries of life’s origins
Recent experiments and simulations are starting to answer some fundamental questions about how life came to be.
Image credit: Shutterstock/Radoslaw Lecyk.
Cave in coastal Kenya with tree growing in the middle.
Journal Club: Small, sharp blades mark shift from Middle to Later Stone Age in coastal Kenya
Archaeologists have long tried to define the transition between the two time periods.
Image credit: Ceri Shipton.
Illustration of groups of people chatting
Exploring the length of human conversations
Adam Mastroianni and Daniel Gilbert explore why conversations almost never end when people want them to.
Listen
Past PodcastsSubscribe
Panda bear hanging in a tree
How horse manure helps giant pandas tolerate cold
A study finds that giant pandas roll in horse manure to increase their cold tolerance.
Image credit: Fuwen Wei.

Similar Articles

Site Logo
Powered by HighWire
  • Submit Manuscript
  • Twitter
  • Facebook
  • RSS Feeds
  • Email Alerts

Articles

  • Current Issue
  • Special Feature Articles – Most Recent
  • List of Issues

PNAS Portals

  • Anthropology
  • Chemistry
  • Classics
  • Front Matter
  • Physics
  • Sustainability Science
  • Teaching Resources

Information

  • Authors
  • Editorial Board
  • Reviewers
  • Subscribers
  • Librarians
  • Press
  • Cozzarelli Prize
  • Site Map
  • PNAS Updates
  • FAQs
  • Accessibility Statement
  • Rights & Permissions
  • About
  • Contact

Feedback    Privacy/Legal

Copyright © 2021 National Academy of Sciences. Online ISSN 1091-6490