Light-Driven Chloride Transport Kinetics of Halorhodopsin.

Biophysical Journal
Hasin FerozManish Kumar

Abstract

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.

Citations

May 1, 2021·Biochimica Et Biophysica Acta. Biomembranes·Hasin FerozManish Kumar
Nov 14, 2021·Chembiochem : a European Journal of Chemical Biology·Na DuKai Liu

❮ Previous
Next ❯

Related Concepts

Related Feeds

Bacterial Metabolism

Baterial metabolism is how bacteria obtain the energy and nutrients they need to live and reproduce.The study of bacterial metabolism focuses on the chemical diversity of substrate oxidations and dissimilation reactions (reactions by which substrate molecules are broken down), which normally function in bacteria to generate energy. Also within the scope of bacterial metabolism is the study of the uptake and utilization of the inorganic or organic compounds required for growth and maintenance of a cellular steady state (assimilation reactions). Discover the latest research on bacterial metabolism here.