Conformational cycle and ion-coupling mechanism of the Na + /hydantoin transporter Mhp1

• DOI: 10.1073/pnas.1410431111
• Publication Date: 2014-09-30T15:28:38Z
• Authors: Kelli Kazmier; Shruti Sharma; Shahidul M. Islam; Benoît Roux; Hassane S. Mchaourab
• Keywords: Conformational change

Significance Na + -coupled symporters use the cellular gradient to power transport of physiologically important molecules across lipid membrane. However, mechanism by which binding and dissociation drive remains undefined. This work investigated /hydantoin transporter Mhp1, a member LeuT-fold class transporters, describe conformations sampled during its cycle elucidate ligand-induced shifts in conformational equilibrium. The results this study suggest that Mhp1 isomerization between inward- outward-facing are -independent coupling occurs through modulation substrate affinity coordination. A previously unidentified model defined ligand-independent equilibrium fluctuations emerges from work, offering new perspective on symport LeuT-fold.