TY  - JOUR
A1  - Feroz, Hasin
A1  - Ferlez, Bryan
A1  - Lefoulon, Cecile
A1  - Ren, Tingwei
A1  - Baker, Carol S.
A1  - Gajewski, John P.
A1  - Lugar, Daniel J.
A1  - Gaudana, Sandeep B.
A1  - Butler, Peter J.
A1  - Hühn, Jonas
A1  - Lamping, Matthias
A1  - Parak, Wolfgang J.
A1  - Hibberd, Julian M.
A1  - Kerfeld, Cheryl A.
A1  - Smirnoff, Nicholas
A1  - Blatt, Michael R.
A1  - Golbeck, John H.
A1  - Kumar, Manish
T1  - Light-Driven Chloride Transport Kinetics of Halorhodopsin
JF  - Biophysical Journal
N2  - Despite growing interest in light-driven ion pumps for use in optogenetics, current estimates of their transport rates span two orders of magnitude due to challenges in measuring slow transport processes and determining protein concentration and/or orientation in membranes in vitro. In this study, we report, to our knowledge, the first direct quantitative measurement of light-driven Cl− transport rates of the anion pump halorohodopsin from Natronomonas pharaonis (NpHR). We used light-interfaced voltage clamp measurements on NpHR-expressing oocytes to obtain a transport rate of 219 (± 98) Cl−/protein/s for a photon flux of 630 photons/protein/s. The measurement is consistent with the literature-reported quantum efficiency of ∼30% for NpHR, i.e., 0.3 isomerizations per photon absorbed. To reconcile our measurements with an earlier-reported 20 ms rate-limiting step, or 35 turnovers/protein/s, we conducted, to our knowledge, novel consecutive single-turnover flash experiments that demonstrate that under continuous illumination, NpHR bypasses this step in the photocycle.
KW  - Optogenetics
Y1  - 2018
UR  - https://www.cell.com/biophysj/fulltext/S0006-3495(18)30685-4
U6  - http://dx.doi.org/10.1016/j.bpj.2018.06.009
SN  - 1542-0086
VL  - 115
IS  - 2
SP  - 353
EP  - 360
ER  -