Exploring the Substrate Specificity of a Sugar Transporter with Biosensors and Cheminformatics

Area of Science:

• Plant biology
• Molecular biology
• Biotechnology

Background:

• Sugar transporters, known as SWEETs (Sugars Will Eventually be Exported Transporters), are vital for plant physiological processes and biotechnological applications.
• Plant genomes typically contain around 20 SWEET paralogs, categorized into four distinct clades, with varying substrate preferences (hexoses vs. sucrose).
• The precise molecular determinants governing substrate recognition by SWEET transporters remain incompletely understood.

Purpose of the Study:

• To investigate the structural requirements for substrate recognition by SWEET sugar transporters.
• To identify novel sugar substrates recognized by SWEET transporters.
• To explore the potential of combining biosensor technology with computational methods for characterizing transporter specificity.

Main Methods:

• Utilized SweetTrac1, a biosensor derived from *Arabidopsis thaliana* SWEET1, which translates substrate binding into a measurable fluorescence signal.
• Performed a small-molecule screen employing the SweetTrac1 biosensor to identify responsive compounds.
• Integrated cheminformatics analysis with biosensor screening data to analyze substrate recognition patterns.
• Validated cellular uptake of identified substrates using the wild-type SWEET transporter.

Main Results:

• The SweetTrac1 biosensor successfully identified 12 novel sugars and their derivatives capable of interacting with the transporter.
• Demonstrated that SWEET transporters can recognize a diverse range of sugar forms, including furanoses, pyranoses, and acyclic structures.
• Confirmed cellular uptake mediated by the wild-type transporter for three identified compounds, notably including the antidiabetic drugs 1-deoxynojirimycin and voglibose.

Conclusions:

• SWEET transporters exhibit broad substrate specificity, accommodating various sugar configurations beyond simple hexoses or sucrose.
• The combination of biosensor technology and cheminformatics provides a powerful approach for dissecting transporter-substrate interactions.
• Findings contribute to understanding sugar transport mechanisms and have implications for drug development targeting SWEETs.