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Bacterial nitrogen metabolism and ammonium uptake

Reference	BBS/E/J/00000013
Principal Investigator / Supervisor	Professor Mike Merrick
Co-Investigators / Co-Supervisors
Institution	John Innes Centre
Department	John Innes Centre Department
Funding type	Research
Value (£)	1,628,502
Status	Completed
Type	Institute Project
Start date	01/01/2000
End date	02/07/2013
Duration	162 months

Abstract

Bacteria can use a wide range of organic and inorganic sources of nitrogen. This project aims to elucidate the molecular mechanisms that ensure the coordination of cellular nitrogen metabolism, at the levels of both gene transcription and protein activity. We aim to understand how these respond to availability of nitrogen both outside and inside the cell. Our studies focus on two key families of proteins: the signal transducing PII proteins and the ammonia channel proteins. PII proteins are found in all prokaryotes and in plants where they sense the intracellular N status. Our studies focus on how they interact with a variety of target proteins to control such functions as nitrogen fixation and uptake of ammonium into cells. A key to these processes is the ability of PII proteins to bind 2-oxglutarate and ATP/ADP and we are studying the effects of these molecules on PII structure. The transport of ammonium across cell membranes is a fundamental process in living organisms and ammonia channel (Amt) proteins are found in all domains of life. Our work on Amt proteins in Rhizobium etli showed the significance of cellular nitrogen status in regulating an effective symbiosis with the host legume. In recent work we have pioneered the use of the Escherichia coli AmtB protein, as a model system to study the mode of action of ammonia channels. We have used AmtB to explore the molecular mechanism of these proteins. We have also shown that in prokaryotes ammonia flux through Amt proteins is controlled by a PII protein called GlnK, and we have determined the X-ray structure of the AmtB-GlnK complex. Current studies focus on how this complex is regulated by the intracellular nitrogen status. In higher animals, including humans, ammonia channels are represented by the Rhesus proteins. We solved the first Rhesus protein structure using a rare bacterial Rh protein from Nitrosomonas europeaea, and this work had direct translational significance for studies of the human Rh complex.

Summary

unavailable

Committee	Closed Committee - Plant & Microbial Sciences (PMS)
Research Topics	Microbiology, Soil Science
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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