Glutamate-194 to cysteine mutation inhibits fast light-induced proton release in bacteriorhodopsin

Biochemistry. 1997 Jul 22;36(29):8671-6. doi: 10.1021/bi970744y.


Substitution of glutamic acid-194, a residue on the extracellular surface of bacteriorhodopsin, with a cysteine inhibits the fast light-induced proton release that normally is coupled with the deprotonation of the Schiff base during the L to M transition. Proton release in this mutant occurs at the very end of the photocycle and coincides with deprotonation of the primary proton acceptor, Asp-85, during the O to bR transition. the E194C mutation also results in a slowing down of the photocycle by about 1 order of magnitude as compared to the wild type and produces a strong effect on the pH dependence of dark adaptation that is interpreted as a drastic reduction or elimination of the coupling between the primary proton acceptor Asp-85 and the proton release group. These data indicate that Glu-194 is a critical component of the proton release complex in bacteriorhodopsin.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacteriorhodopsins / metabolism*
  • Cysteine / genetics*
  • Dark Adaptation
  • Glutamic Acid / genetics*
  • Halobacterium
  • Hydrogen-Ion Concentration
  • Kinetics
  • Light*
  • Mutation
  • Protons*
  • Spectrophotometry, Atomic


  • Protons
  • Glutamic Acid
  • Bacteriorhodopsins
  • Cysteine