TY - JOUR
T1 - Electric-field-induced Schiff-base deprotonation in D85N mutant bacteriorhodopsin
AU - Kolodner, Paul
AU - Lukashev, Evgeniy P.
AU - Ching, Yuan Chin
AU - Rousseau, Denis L.
PY - 1996/10/15
Y1 - 1996/10/15
N2 - The application of an external electric field to dry films of Asp-85 → Asn mutant bacteriorhodopsin causes deprotonation of the Schiff base, resulting in a shift of the optical absorption maximum from 600 nm to 400 nm. This is in marked contrast to the case of wild-type bacteriorhodopsin films, in which electric fields produce a red-shifted product whose optical properties are similar to those of the acid-blue form of the protein. This difference is due to the much weaker binding of the Schiff-base proton in the mutant protein, as indicated by its low pK of ≃9, as compared with the value pK ≃ 13 in the wild type. Other bacteriorhodopsins with lowered Schiff-base pK values should also exhibit a field-induced shift in the protonation equilibrium of the Schiff base. We propose mechanisms to account for these observations.
AB - The application of an external electric field to dry films of Asp-85 → Asn mutant bacteriorhodopsin causes deprotonation of the Schiff base, resulting in a shift of the optical absorption maximum from 600 nm to 400 nm. This is in marked contrast to the case of wild-type bacteriorhodopsin films, in which electric fields produce a red-shifted product whose optical properties are similar to those of the acid-blue form of the protein. This difference is due to the much weaker binding of the Schiff-base proton in the mutant protein, as indicated by its low pK of ≃9, as compared with the value pK ≃ 13 in the wild type. Other bacteriorhodopsins with lowered Schiff-base pK values should also exhibit a field-induced shift in the protonation equilibrium of the Schiff base. We propose mechanisms to account for these observations.
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U2 - 10.1073/pnas.93.21.11618
DO - 10.1073/pnas.93.21.11618
M3 - Article
C2 - 8876185
AN - SCOPUS:0029908199
SN - 0027-8424
VL - 93
SP - 11618
EP - 11621
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 21
ER -