TY - JOUR
T1 - The Environment Shapes the Inner Vestibule of LeuT
AU - Sohail, Azmat
AU - Jayaraman, Kumaresan
AU - Venkatesan, Santhoshkannan
AU - Gotfryd, Kamil
AU - Daerr, Markus
AU - Gether, Ulrik
AU - Loland, Claus J
AU - Wanner, Klaus T
AU - Freissmuth, Michael
AU - Sitte, Harald H
AU - Sandtner, Walter
AU - Stockner, Thomas
PY - 2016/11
Y1 - 2016/11
N2 - Human neurotransmitter transporters are found in the nervous system terminating synaptic signals by rapid removal of neurotransmitter molecules from the synaptic cleft. The homologous transporter LeuT, found in Aquifex aeolicus, was crystallized in different conformations. Here, we investigated the inward-open state of LeuT. We compared LeuT in membranes and micelles using molecular dynamics simulations and lanthanide-based resonance energy transfer (LRET). Simulations of micelle-solubilized LeuT revealed a stable and widely open inward-facing conformation. However, this conformation was unstable in a membrane environment. The helix dipole and the charged amino acid of the first transmembrane helix (TM1A) partitioned out of the hydrophobic membrane core. Free energy calculations showed that movement of TM1A by 0.30 nm was driven by a free energy difference of ~15 kJ/mol. Distance measurements by LRET showed TM1A movements, consistent with the simulations, confirming a substantially different inward-open conformation in lipid bilayer from that inferred from the crystal structure.
AB - Human neurotransmitter transporters are found in the nervous system terminating synaptic signals by rapid removal of neurotransmitter molecules from the synaptic cleft. The homologous transporter LeuT, found in Aquifex aeolicus, was crystallized in different conformations. Here, we investigated the inward-open state of LeuT. We compared LeuT in membranes and micelles using molecular dynamics simulations and lanthanide-based resonance energy transfer (LRET). Simulations of micelle-solubilized LeuT revealed a stable and widely open inward-facing conformation. However, this conformation was unstable in a membrane environment. The helix dipole and the charged amino acid of the first transmembrane helix (TM1A) partitioned out of the hydrophobic membrane core. Free energy calculations showed that movement of TM1A by 0.30 nm was driven by a free energy difference of ~15 kJ/mol. Distance measurements by LRET showed TM1A movements, consistent with the simulations, confirming a substantially different inward-open conformation in lipid bilayer from that inferred from the crystal structure.
U2 - 10.1371/journal.pcbi.1005197
DO - 10.1371/journal.pcbi.1005197
M3 - Journal article
C2 - 27835643
SN - 1553-734X
VL - 12
JO - P L o S Computational Biology (Online)
JF - P L o S Computational Biology (Online)
IS - 11
M1 - e1005197
ER -