TY - JOUR
T1 - Histidine residues regulate the transition of photoexcited rhodopsin to its active conformation, metarhodopsin II
AU - Weitz, Charles J.
AU - Nathans, Jeremy
N1 - Funding Information:
We wish to thank C. Gorman, A. Levinson, and R. Kline for the pClS vector and 293s cell line, L. Stryer and Hoffmann-La Roche Inc. for II-cis-retinal, P. Hargrave for MAb B&30, K. P. Hofmann, J. Korenbrot, Y. Koutalis, and G. Yellen for helpful discussions and I. Chiu, S. Merbs, K.-Y. Yau, and C. Yellen for critical comments on the manuscript. C. J. W. is a recipient of a Physician Scientist Award from the National Eye Institute. This work was supportedbytheHowardHughesMedicallnstituteandtheNlH. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 USC Section 1734 solely to indicate this fact.
PY - 1992/3
Y1 - 1992/3
N2 - The biologically active photoproduct of rhodopsin, metarhodopsin II (M II), exists in a pH-sensitive equilibrium with its precursor, metarhodopsin I (M I). Increasing acidity favors M 11, with the midpoint of the pH titration curve at pH 6.4. To test the long-standing proposal that histidine protonation regulates this conformational transition, we characterized mutant rhodopsins in which each of the 6 histidines was replaced by phenylalanine or cysteine. Only mutants substituted at the 3 conserved histidines showed abnormal M I-M II equilibria. Those in which His-211 was replaced by phenylalanine or cysteine formed little or no M 11 at either extreme of pH, whereas mutants substituted at His-65 or at His-152 showed enhanced sensitivity to protons. The simplest interpretation of these results is that His-211 is the site where protonation strongly stabilizes the M I I conformation and that His-65 and His-152 are sites where protonation modestly destabilizes the M 11 conformation.
AB - The biologically active photoproduct of rhodopsin, metarhodopsin II (M II), exists in a pH-sensitive equilibrium with its precursor, metarhodopsin I (M I). Increasing acidity favors M 11, with the midpoint of the pH titration curve at pH 6.4. To test the long-standing proposal that histidine protonation regulates this conformational transition, we characterized mutant rhodopsins in which each of the 6 histidines was replaced by phenylalanine or cysteine. Only mutants substituted at the 3 conserved histidines showed abnormal M I-M II equilibria. Those in which His-211 was replaced by phenylalanine or cysteine formed little or no M 11 at either extreme of pH, whereas mutants substituted at His-65 or at His-152 showed enhanced sensitivity to protons. The simplest interpretation of these results is that His-211 is the site where protonation strongly stabilizes the M I I conformation and that His-65 and His-152 are sites where protonation modestly destabilizes the M 11 conformation.
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U2 - 10.1016/0896-6273(92)90274-H
DO - 10.1016/0896-6273(92)90274-H
M3 - Article
C2 - 1532320
AN - SCOPUS:0026548090
SN - 0896-6273
VL - 8
SP - 465
EP - 472
JO - Neuron
JF - Neuron
IS - 3
ER -