PDBsum entry 3f3c

Transport protein

PDB id: 3f3c

Contents

Protein chain

509 a.a. *

Ligands

PFF

BOG ×5

Metals

_NA ×2

Waters ×88

* Residue conservation analysis

PDB id:

3f3c

Name:

Transport protein

Title:

Crystal structure of leut bound to 4-fluoro-l-phenylalanine and sodium

Structure:

Transporter. Chain: a. Synonym: leucine transporter. Engineered: yes

Source:

Aquifex aeolicus. Organism_taxid: 63363. Strain: vf5. Gene: snf, aq_2077. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.10Å R-factor: 0.198 R-free: 0.237

Authors:

S.K.Singh,C.L.Piscitelli,A.Yamashita,E.Gouaux

Key ref:

S.K.Singh et al. (2008). A competitive inhibitor traps LeuT in an open-to-out conformation. Science, 322, 1655-1661. PubMed id: 19074341 DOI: 10.1126/science.1166777

Date:

30-Oct-08 Release date: 23-Dec-08

Protein chain

O67854  (O67854_AQUAE) -  Na(+):neurotransmitter symporter (Snf family) from Aquifex aeolicus (strain VF5)

Seq: 513 a.a.

Struc: 509 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1126/science.1166777

Science 322:1655-1661 (2008)

PubMed id: 19074341

A competitive inhibitor traps LeuT in an open-to-out conformation.

S.K.Singh, C.L.Piscitelli, A.Yamashita, E.Gouaux.

ABSTRACT

Secondary transporters are workhorses of cellular membranes, catalyzing the movement of small molecules and ions across the bilayer and coupling substrate passage to ion gradients. However, the conformational changes that accompany substrate transport, the mechanism by which a substrate moves through the transporter, and principles of competitive inhibition remain unclear. We used crystallographic and functional studies on the leucine transporter (LeuT), a model for neurotransmitter sodium symporters, to show that various amino acid substrates induce the same occluded conformational state and that a competitive inhibitor, tryptophan (Trp), traps LeuT in an open-to-out conformation. In the Trp complex, the extracellular gate residues arginine 30 and aspartic acid 404 define a second weak binding site for substrates or inhibitors as they permeate from the extracellular solution to the primary substrate site, which demonstrates how residues that participate in gating also mediate permeation.

Selected figure(s)

Figure 4.
Fig. 4. A second Trp molecule is bound between R30 and D404 of the extracellular gate only in the open-to-out conformation. (A) Trp602 bound in the extracellular vestibule of LeuT, residing between D404 and R30, flanked by the -helix in TM10. (B) Extracellular vestibule of the LeuT-SeMet complex. Anomalous-difference Fourier map (contoured at 5 and 15 and depicted in green and blue mesh, respectively) showing no substantial density peaks in the extracellular vestibule.

Figure 5.
Fig. 5. Schematic of transport and inhibition in LeuT. Postulated conformational changes associated with isomerization from the open-to-out (A) to the outward-facing occluded state (B) on binding of substrate and ions, from the occluded (B) to open-to-in state (C) and dissociation of transported substrate and ions, and from the open-to-in (C) back to the open-to-out state (A). (D) Effect of the competitive inhibitor Trp on transport: stabilizing the open-to-out conformation. (E) Effect of the noncompetitive TCA inhibitors on transport-stabilizing the outward-facing occluded conformation. The boxed conformations represent actual crystal structures, whereas the unboxed conformations are hypothetical.

The above figures are reprinted by permission from the AAAs: Science (2008, 322, 1655-1661) copyright 2008.

Figures were selected by an automated process.