Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.
Subscribe

Logo for

21 (4): 536-545

Copyright © 2002 by the European Molecular Biology Organization.

Membrane sequestration of the signal transduction protein GlnK by the ammonium transporter AmtB

Graham Coutts, Gavin Thomas1, Dan Blakey, and Mike Merrick2

Department of Molecular Microbiology, John Innes Centre, Norwich NR4 7UH, UK 1Present address: Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK 2Corresponding author e-mail: mike.merrick{at}bbsrc.ac.uk

Abstract: The Amt proteins are ammonium transporters that are conserved throughout all domains of life, being found in bacteria, archaea and eukarya. In bacteria and archaea, the Amt structural genes (amtB) are invariably linked to glnK, which encodes a member of the PII signal transduction protein family, proteins that regulate enzyme activity and gene expression in response to the intracellular nitrogen status. We have now shown that in Escherichia coli and Azotobacter vinelandii, GlnK binds to the membrane in an AmtB-dependent manner and that GlnK acts as a negative regulator of the transport activity of AmtB. Membrane binding is dependent on the uridylylation state of GlnK and is modulated according to the cellular nitrogen status such that it is maximal in nitrogen-sufficient situations. The membrane sequestration of GlnK by AmtB represents a novel form of signal transduction in which an integral membrane transport protein functions to link the extracellular ammonium concentration to the intracellular responses to nitrogen status. The results also offer new insights into the evolution of PII proteins and a rationale for their trigonal symmetry.

Key Words: Keywords: ammonium transport/membrane sequestration/nitrogen regulation/PII regulatory proteins/signal transduction

To Advertise     Find Products

Science Signaling. ISSN 1937-9145 (online), 1945-0877 (print). Pre-2008: Science's STKE. ISSN 1525-8882