Visualizing multistep elevator-like transitions of a nucleoside transporter.

Area of Science:

• Biochemistry
• Structural Biology
• Membrane Transport

Background:

• Membrane transporters facilitate substrate movement across cellular membranes via alternating access.
• The elevator mechanism is an emerging model where a transport domain moves across the membrane.
• Previous studies lacked detailed structural information on the conformational transitions within this mechanism.

Purpose of the Study:

• To elucidate the conformational pathway of the elevator mechanism in membrane transport.
• To characterize the intermediate states of a concentrative nucleoside transporter.

Main Methods:

• X-ray crystallography was employed to determine the structures of the transporter.
• Structures of inward-facing, intermediate, and outward-facing states were resolved.
• Multiple intermediate conformations were analyzed.

Main Results:

• Crystal structures captured the transport domain at various stages of its elevator motion.
• Multiple intermediate conformations revealed a detailed trajectory of the conformational transition.
• State-dependent conformational changes within the transport domain were identified.

Conclusions:

• The study presents a comprehensive trajectory of the elevator mechanism, moving beyond static end states.
• Detailed structural insights into intermediate conformations advance the understanding of membrane transporter dynamics.
• Findings provide a mechanistic basis for the elevator-like motion in nucleoside transporters.