View of the AmtB-GlnK complex
By establishing the structure of a protein complex we come closer to understanding how it works. The surface of AmtB is shown, and GlnK is shown drawn in red and green. Each subunit of AmtB and GlnK is coloured independently.

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Another piece of membrane protein puzzle solved; how cells regulate ammonium uptake can be better understood.

January 2007

Nitrogen uptake and metabolism is essential for living cells. The uptake mainly occurs through the most reduced form of nitrogen, ammonia. When nitrogen is limited, ammonia uptake in bacteria, fungi and plants is facilitated by a family of membrane proteins known as the ammonium transport (Amt) family. Work on this ubiquitous protein family has been pioneered by studies in the laboratory of Dr. Mike Merrick in the Department of Molecular Microbiology at JIC, using the bacterium Escherichia coli as a simple model system.

In collaboration with researchers at the University of Sheffield and the Paul Scherrer Institute in Switzerland, Dr. Merrick’s group have now elucidated how bacteria control the entry of ammonia into cells. They have determined the crystal structure of a complex between the ammonia channel AmtB and its regulatory protein GlnK. This marks a significant advance in understanding of the process of nitrogen regulation in prokaryotic cells. (Prokaryotes are organisms without a cell nucleus). These results were recently published in the journal: Proceedings of the National Academy of Sciences of the U.S.A. and can be read at

http://www.pnas.org/cgi/content/abstract/0610348104v1