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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Exploring Conformational Transitions and Free-Energy Profiles of Proton-Coupled Oligopeptide Transporters

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Batista, Mariana R. B. [1] ; Watts, Anthony [2] ; Costa-Filho, Antonio Jose [1]
Total Authors: 3
[1] Univ Sao Paulo, Ribeirao Preto Sch Philosophy Sci & Letters, BR-14040901 Ribeirao Preto, SP - Brazil
[2] Univ Oxford, Dept Biochem, South Parks Rd, Oxford OX1 2JD - England
Total Affiliations: 2
Document type: Journal article
Source: JOURNAL OF CHEMICAL THEORY AND COMPUTATION; v. 15, n. 11, p. 6433-6443, NOV 2019.
Web of Science Citations: 0

Proteins involved in peptide uptake and transport belong to the proton-coupled oligopeptide transporter (POT) family. Crystal structures of POT family members reveal a common fold consisting of two domains of six transmembrane alpha helices that come together to form a ``V{''} shaped transporter with a central substrate binding site. Proton-coupled oligopeptide transporters operate through an alternate access mechanism, where the membrane transporter undergoes global conformational changes, alternating between inward-facing (IF), outward-facing (OF), and occluded (OC) states. Conformational transitions are promoted by proton and ligand binding; however, due to the absence of crystallographic models of the outward-open state, the role of H+ and ligands is still not fully understood. To provide a comprehensive picture of the POT conformational equilibrium, conventional and enhanced sampling molecular dynamics simulations of PepT(st) in the presence or absence of ligand and protonation were performed. Free-energy profiles of the conformational variability of PepT(st) were obtained from microseconds of adaptive biasing force (ABF) simulations. Our results reveal that both proton and ligand significantly change the conformational free-energy landscape. In the absence of ligand and protonation, only transitions involving IF and OC states are allowed. After protonation of the residue Glu300, the wider free-energy well for Glu300 protonated PepT(st) indicates a greater conformational variability relative to the apo system, and OF conformations became accessible. For the Glu300 protonated Holo-PepT(st), the presence of a second free-energy minimum suggests that OF conformations are not only accessible, but also stable. The differences in the free-energy profiles demonstrate that transitions toward outward-facing conformation occur only after protonation, which is likely the first step in the mechanism of peptide transport. Our extensive ABF simulations provide a fully atomic description of all states of the transport process, offering a model for the alternating access mechanism and how protonation and ligand control the conformational changes. (AU)

FAPESP's process: 16/16328-3 - Molecular dynamics simulations of proton dependent oligopeptide transporters
Grantee:Mariana Raquel Bunoro Batista
Support Opportunities: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 15/50366-7 - Resolving mechanistic details of peptide transport across membranes using crystallographic and non-crystallographic structural biology approaches
Grantee:Antonio José da Costa Filho
Support Opportunities: Regular Research Grants