Single glucose molecule transport process revealed by force tracing and molecular dynamics simulations

Area of Science:

• Cellular Biology
• Biophysics
• Molecular Transport Mechanisms

Background:

• Cell membrane transport is vital for metabolism.
• Previous structural studies lacked dynamic, single-molecule transport insights.
• Understanding transporter mechanisms at the molecular level remains challenging.

Purpose of the Study:

• To directly monitor single d-glucose molecule transport across living cell membranes.
• To elucidate the dynamic mechanism and forces involved in glucose transport.
• To identify key molecular interactions within glucose transporter 1 (GLUT1).

Main Methods:

• Atomic force microscopy (AFM)-based force tracing was employed.
• Molecular dynamics (MD) simulations were used to calculate force profiles.
• Biological experiments validated the role of identified salt bridges.

Main Results:

• Single d-glucose transport requires 37 ± 9 pN force, takes ~20 ms, and occurs at ~0.3 μm/s.
• MD simulations quantitatively matched AFM force tracing data.
• Two specific salt bridges (K38/E299 and K300/E426) in GLUT1 were identified as critical for transport.

Conclusions:

• Provided the first unambiguous, single-molecule description of glucose transport across cell membranes.
• Demonstrated the crucial role of identified salt bridges in GLUT1-mediated glucose transport.
• Integrated biophysical techniques with molecular simulations for mechanistic insights.