Nitrogen regulation of protein–protein interactions and transcript levels of GlnK PII regulator and AmtB ammonium transporter homologs in Archaea
Version of Record online: 28 AUG 2013
© 2013 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Volume 2, Issue 5, pages 826–840, October 2013
How to Cite
MicrobiologyOpen 2013; 2(5): 826–840
- Issue online: 8 OCT 2013
- Version of Record online: 28 AUG 2013
- Manuscript Accepted: 12 JUL 2013
- Manuscript Revised: 3 JUL 2013
- Manuscript Received: 24 APR 2013
- Spanish Ministry of Science and Innovation. Grant Number: BIO2008-00082
- European Union
- Spanish Ministry of Education. Grant Number: AP2007-02932
- National Institute of General Medical Science. Grant Number: NIH R01 GM057498
- Basic Energy Sciences (BES)
- U.S. Department of Energy (DOE)
Gene homologs of GlnK PII regulators and AmtB-type ammonium transporters are often paired on prokaryotic genomes, suggesting these proteins share an ancient functional relationship. Here, we demonstrate for the first time in Archaea that GlnK associates with AmtB in membrane fractions after ammonium shock, thus, providing a further insight into GlnK-AmtB as an ancient nitrogen sensor pair. For this work, Haloferax mediterranei was advanced for study through the generation of a pyrE2-based counterselection system that was used for targeted gene deletion and expression of Flag-tagged proteins from their native promoters. AmtB1-Flag was detected in membrane fractions of cells grown on nitrate and was found to coimmunoprecipitate with GlnK after ammonium shock. Thus, in analogy to bacteria, the archaeal GlnK PII may block the AmtB1 ammonium transporter under nitrogen-rich conditions. In addition to this regulated protein–protein interaction, the archaeal amtB-glnK gene pairs were found to be highly regulated by nitrogen availability with transcript levels high under conditions of nitrogen limitation and low during nitrogen excess. While transcript levels of glnK-amtB are similarly regulated by nitrogen availability in bacteria, transcriptional regulators of the bacterial glnK promoter including activation by the two-component signal transduction proteins NtrC (GlnG, NRI) and NtrB (GlnL, NRII) and sigma factor σN (σ54) are not conserved in archaea suggesting a novel mechanism of transcriptional control.