Selective Translocation of Cyclic Sugars through Dynamic Bacterial Transporter

Area of Science:

• Biophysics
• Molecular Biology
• Nanotechnology

Background:

• Selective molecular translocation through membrane pores is crucial for cellular function.
• Bacterial sugar transporters, like CymA, play vital roles in nutrient uptake and cellular regulation.
• Understanding the structural dynamics of transport proteins is key to elucidating transport mechanisms.

Purpose of the Study:

• To investigate the translocation kinetics of cyclic sugars through the bacterial sugar transporter CymA.
• To determine the role of CymA's dynamic N-terminus in regulating sugar transport.
• To explore the potential of native CymA as a nanopore sensor for single-molecule sugar detection.

Main Methods:

• Single-channel recordings were employed to quantify translocation kinetics.
• Native and truncated CymA (lacking the N-terminus) were used to assess the N-terminus's role.
• Various cyclic sugars differing in charge, size, and symmetry were tested.
• Liposome assays were conducted to corroborate findings.

Main Results:

• Chemically diverse cyclic hexasaccharides translocated effectively through both native and truncated CymA, with faster translocation through truncated CymA.
• Larger cyclic heptasaccharides and octasaccharides bound but did not translocate, indicating size and charge limitations.
• Binding kinetics revealed distinct interactions influenced by molecular properties, consistent with liposome assay results.
• The N-terminus was suggested to regulate transport rate by residing within the CymA barrel.

Conclusions:

• The N-terminus of CymA dynamically regulates the translocation rate of cyclic sugars.
• Native CymA functions as a high-resolution nanopore sensor for simultaneous, single-molecule detection of various sugars.
• CymA's versatile functionality presents significant potential for nanobiotechnology and fundamental transport mechanism studies.