Molecular Basis of the Glucose Transport Mechanism in Plants

Balaji Selvam, Ya Chi Yu, Liqing Chen, Diwakar Shukla

Research output: Contribution to journalArticle

Abstract

The SWEET family belongs to a class of transporters in plants that undergoes large conformational changes to facilitate transport of sugar molecules across the cell membrane (SWEET, Sugars Will Eventually Be Exported Transporter). However, the structures of their functionally relevant conformational states in the transport cycle have not been reported. In this study, we have characterized the conformational dynamics and complete transport cycle of glucose in the OsSWEET2b transporter using extensive molecular dynamics simulations. Using Markov state models, we estimated the free energy barrier associated with different states as well as for the glucose transport mechanism. SWEETs undergo a structural transition to outward-facing (OF), occluded (OC), and inward-facing (IF) and strongly support an alternate access transport mechanism. The glucose diffuses freely from outside to inside the cell without causing major conformational changes which means that the conformations of glucose unbound and bound snapshots are exactly the same for OF, OC, and IF states. We identified a network of hydrophobic core residues at the center of the transporter that restricts the glucose entry to the cytoplasmic side and acts as an intracellular hydrophobic gate. The mechanistic predictions from molecular dynamics simulations are validated using site-directed mutagenesis experiments. Our simulation also revealed hourglass-like intermediate states making the pore radius narrower at the center. This work provides new fundamental insights into how substrate-transporter interactions actively change the free energy landscape of the transport cycle to facilitate enhanced transport activity.

Original languageEnglish (US)
Pages (from-to)1085-1096
Number of pages12
JournalACS Central Science
Volume5
Issue number6
DOIs
StatePublished - Jun 26 2019

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Facings
Glucose
Sugars
Free energy
Molecular dynamics
Mutagenesis
Facilitative Glucose Transport Proteins
Energy barriers
Computer simulation
Cell membranes
Conformations
Molecules
Substrates
Experiments

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)

Cite this

Molecular Basis of the Glucose Transport Mechanism in Plants. / Selvam, Balaji; Yu, Ya Chi; Chen, Liqing; Shukla, Diwakar.

In: ACS Central Science, Vol. 5, No. 6, 26.06.2019, p. 1085-1096.

Research output: Contribution to journalArticle

Selvam, Balaji ; Yu, Ya Chi ; Chen, Liqing ; Shukla, Diwakar. / Molecular Basis of the Glucose Transport Mechanism in Plants. In: ACS Central Science. 2019 ; Vol. 5, No. 6. pp. 1085-1096.
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