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Cloning of a cDNA coding for an amino acid carrier from Ricinus communis (RcAAP1) by functional complementation in
A C Marvier1, A Neelam, J A Bick
1School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton S016 7PX, UK.
Biochimica Et Biophysica Acta
|September 12, 1998
Summary
Researchers identified the Ricinus communis amino acid permease 1 (RcAAP1) gene. This gene facilitates histidine uptake, with lysine and arginine also identified as substrates, offering insights into plant amino acid transport.
Area of Science:
- Plant Molecular Biology
- Biochemistry
- Membrane Transport
Background:
- Amino acid permeases are crucial for nutrient uptake in plants.
- Understanding substrate specificity is key to optimizing plant nutrition and development.
- Ricinus communis (castor bean) is an important oilseed crop with unique metabolic pathways.
Purpose of the Study:
- To isolate and characterize the amino acid permease gene RcAAP1 from Ricinus communis.
- To determine the kinetic properties and substrate specificity of the RcAAP1 permease.
- To elucidate the role of RcAAP1 in histidine transport and its interaction with other amino acids.
Main Methods:
- Isolation of RcAAP1 cDNA using yeast complementation.
- Detailed kinetic analysis of RcAAP1-mediated histidine uptake.
- Substrate specificity investigation through competitive inhibition assays and direct uptake measurements.
Main Results:
- RcAAP1 cDNA encodes a 53.1 kDa protein with 486 amino acids.
- Histidine uptake by RcAAP1 is pH-dependent, optimal at acidic pH, and sensitive to protonophores.
- RcAAP1 exhibits broad substrate specificity, with basic amino acids (histidine, lysine, arginine) being preferred substrates, and alanine being the most effective neutral amino acid competitor.
Conclusions:
- RcAAP1 is a high-affinity amino acid transporter in Ricinus communis.
- The transporter shows a preference for basic amino acids, indicating a role in the transport of essential nitrogenous compounds.
- Kinetic and specificity data provide a foundation for further studies on amino acid homeostasis in plants.