Functionally important amino acids in rice sucrose transporter OsSUT1
Ye Sun1, Zi Lin, Anke Reinders
1Department of Plant Biology, University of Minnesota-Twin Cities, St. Paul, Minnesota 55108, United States.
Biochemistry
|March 31, 2012
Summary
Charged amino acids in rice sucrose transporter OsSUT1 are crucial for its function. Mutagenesis revealed specific residues essential for sucrose uptake, highlighting their role in transport mechanisms similar to other major facilitator superfamily proteins.
Area of Science:
- Plant molecular biology
- Membrane transport proteins
- Structural biology
Background:
- The rice sucrose transporter OsSUT1 facilitates sucrose uptake in plants.
- Understanding the molecular mechanisms of sucrose transport is vital for crop improvement.
- Major facilitator superfamily (MFS) proteins share conserved structural features and transport mechanisms.
Purpose of the Study:
- To investigate the role of conserved charged amino acids in the membrane spans of OsSUT1.
- To elucidate the contribution of these residues to sucrose transport activity.
- To compare the functional importance of charged residues in OsSUT1 with other MFS transporters.
Main Methods:
- Utilized a three-dimensional structural model of OsSUT1 based on MFS protein crystal structures.
- Performed site-directed mutagenesis on six conserved charged amino acid residues.
- Conducted biochemical assays to assess sucrose uptake activity and proton (H+) leak.
Main Results:
- Mutagenesis identified key charged residues essential for OsSUT1 function.
- D177N and D331N mutations abolished or severely reduced sucrose transport.
- R188K mutant exhibited uncoupled sucrose and H+ translocation, indicating a role in proton symport.
Conclusions:
- Charged amino acids within membrane spans are critical for the transport mechanism of OsSUT1.
- These findings provide insights into the structure-function relationship of plant sucrose transporters.
- The study reinforces the importance of charged residues in MFS transporter function, as seen in other systems like LacY.
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