Application of Solution nmr spectroscopy to Study Protein Dynamics

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Figure 3. 

Proposed mechanism of the 5-HT3 receptor gating. The graph depicts the 

proposed 

cis-trans

 proline regulatory mechanism of 5-HT3. As shown on top, Helix M2 

and M3 are connected via a flexible loop comprising a proline residue. Mutation of the 

proline residue to other amino acids inactivates the ion transport. Only amino acids that 

significantly allow the population of the 

cis

-form of the backbone yielded functional 

channels that were detected by voltage-clamp experiments. In the bottom, a hypothetical 

structure of the closed and opened transmembrane channel is shown (figure reproduced 

with permission of reference [21]).