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Switching substrate specificity of AMT/MEP/ Rh proteins
Benjamin Neuhäuser1, Marek Dynowski, Uwe Ludewig
1a Institute of Crop Science; Nutritional Crop Physiology ; University of Hohenheim ; Stuttgart , Germany.
Channels (Austin, Tex.)
|December 9, 2014
Summary
Ammonia transporters (AMT/Rh family) facilitate nutrient uptake across cell membranes. This study reviews evidence for different transported substrates, suggesting a common mechanism involving ammonia (NH3) transport.
Area of Science:
- Biochemistry and Molecular Biology
- Membrane Transport
- Microbiology
Background:
- Ammonia (NH3) and ammonium (NH4+) are crucial for organismal growth and are transported by AMT/Rh family proteins across membranes.
- These proteins exhibit conserved structural features and high sequence similarity across all kingdoms of life.
- Despite detailed structural analysis, the exact substrate(s) transported by AMT/Rh proteins remain debated.
Purpose of the Study:
- To review and summarize evidence supporting different substrate transport mechanisms for various AMT/Rh protein classes.
- To discuss how mutations affect the structure and function of these transporters.
- To propose a unified model for ammonium transport mediated by AMT/Rh proteins.
Main Methods:
- Literature review and data synthesis on AMT/Rh protein structure and function.
- Analysis of existing mutational studies and molecular dynamic simulations.
- Comparison of transport mechanisms across different AMT/Rh subfamilies (e.g., AMT1, AMT2, AmtB).
Main Results:
- Evidence is presented for distinct substrate transport models (NH4+, NH3 + H+, NH4+ + H+, or NH3) across different AMT/Rh classes.
- Plant AMT1 transporters are associated with ionic currents, while some AMT2 transporters may transport NH3 without currents.
- Mutational studies reveal altered structure-function relationships.
Conclusions:
- A common transport mechanism involving deprotonation and subsequent NH3 passage through the central pore is proposed for AMT/Rh proteins.
- Understanding the precise transport mechanism is critical for comprehending nutrient assimilation and cellular physiology.
- Further functional studies are needed to definitively establish the transport mechanism.
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