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How sensor Amt-like proteins integrate ammonium signals.
Tobias Pflüger1, Mathias Gschell1, Lin Zhang1
1Faculty of Chemistry and Pharmacy, Institute for Biochemistry, University Freiburg, Albertstr. 21, 79104 Freiburg, Germany.
Science Advances
|June 5, 2024
Summary
Researchers identified the ammonium receptor Sd-Amt1, revealing a unique binding site for two ammonium ions crucial for signal perception. This discovery sheds light on ammonium transport and receptor activation mechanisms.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- Ammonium transporters (Amts) are distinct from aquaporins and potassium channels, uniquely discriminating ammonium.
- This selectivity has enabled their evolutionary repurposing as ammonium receptors.
Purpose of the Study:
- To describe the structure and function of the ammonium receptor Sd-Amt1.
- To elucidate the mechanism of ammonium binding and receptor activation.
Main Methods:
- X-ray crystallography was used to determine the structures of Sd-Amt1 in its ON and OFF states.
- AlphaFold2 prediction was employed to model flexible domains.
Main Results:
- The structure revealed a binding site for two ammonium cations essential for signal perception and receptor activation.
- The sensor domain maintains a trimeric fold, while HAMP domains dimerize the transducer domain upon activation.
- Flexibility was observed in the helices linking the sensor and transducer domains.
Conclusions:
- Sd-Amt1 functions as an ammonium receptor with a unique dual-ammonium binding site.
- Structural insights into the ON and OFF states provide a mechanistic understanding of ammonium sensing and signal transduction.
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