TY  - JOUR
A1  - Bazzone, Andre
A1  - Madej, M. Gregor
A1  - Kaback, H. Ronald
A1  - Fendler, Klaus
T1  - pH regulation of electrogenic sugar/H+ symport in MFS sugar permeases
T2  - PLoS one
N2  - Bacterial sugar symporters in the Major Facilitator Superfamily (MFS) use the H+ (and in a few cases Na+) electrochemical gradients to achieve active transport of sugar into the cell. Because a number of structures of MFS sugar symporters have been solved recently, molecular insight into the transport mechanism is possible from detailed functional analysis. We present here a comparative electrophysiological study of the lactose permease (LacY), the fucose permease (FucP) and the xylose permease (XylE), which reveals common mechanistic principles and differences. In all three symporters energetically downhill electrogenic sugar/H+ symport is observed. Comparison of the pH dependence of symport at symmetrical pH exhibits broad bell-shaped pH profiles extending over 3 to 6 pH units and a decrease at extremely alkaline pH ≥ 9.4 and at acidic to neutral pH = 4.6–7.5. The pH dependence can be described by an acidic to neutral apparent pK (pKapp) and an alkaline pKapp. Experimental evidence suggests that the alkaline pKapp is due to H+ depletion at the protonation site, while the acidic pKapp is due to inhibition of deprotonation. Since previous studies suggest that a single carboxyl group in LacY (Glu325) may be the only side chain directly involved in H+ translocation and a carboxyl side chain with similar properties has been identified in FucP (Asp46) and XylE (Asp27), the present results imply that the pK of this residue is switched during H+/sugar symport in all three symporters.
Y1  - 2016
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/41509
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-415095
UR  - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4882079/
SN  - 1932-6203
N1  - This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
VL  - 11
IS  - (5): e0156392
SP  - 1
EP  - 17
PB  - PLoS
CY  - Lawrence, Kan.
ER  -