Primary Transfer Step in the Light-Driven Ion Pump Bacteriorhodopsin: An Irreversible U-Turn Revealed by Dynamic Nuclear Polarization-Enhanced Magic Angle Spinning NMR.

ABSTRACT: Despite much attention, the path of the highly consequential primary proton transfer in the light-driven ion pump bacteriorhodopsin (bR) remains mysterious. Here we use DNP-enhanced magic angle spinning (MAS) NMR to study critical elements of the active site just before the Schiff base (SB) deprotonates (in the L intermediate), immediately after the SB has deprotonated and Asp85 has become protonated (in the M_o intermediate), and just after the SB has reprotonated and Asp96 has deprotonated (in the N intermediate). An essential feature that made these experiments possible is the 75-fold signal enhancement through DNP. ¹⁵N(SB)-¹H correlations reveal that the newly deprotonated SB is accepting a hydrogen bond from an alcohol and ¹³C-¹³C

SUBMITTER: Ni QZ 

PROVIDER: S-EPMC8313245 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature