Infrared spectroscopic demonstration of a conformational change in bacterorhodopsin involved in proton pumping

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Abstract

Infrared spectral changes in bacteriorhoapsin (bR) were followed during the slow decay of the M intermediate in the temperature region 240-260 K. The decay of the M form is characterized by the disappearance of the thylene bands and the bands indicating the reprotonation of the Schiff base. The route of Schiff-base reprotonation compeletely changes between 240 K and 260 K. At 240 K reprotontion occurs from Asp-85, the group to which the proton was released during M formation, and there is no pumping. At 260 the Schiff-base reprotonation takes place through Asp-96 from the cytoplasmic side, in the normal sequence assumed for proton pumping. The dramatic change in the route of Schiffase reprotonation is coupled to a protein conformational exchange characterized by the change of the ratio of the two amide I bands at 1658 cm-1 and 1669 cm-1. This conforma-tional change is interpreted as the conformational switch fracial for proton pumping: a protein relaxation following M conformatin results in a local rearrangement of the group, in the icinity of the Schiff base. The rearrangement changes the accesibility of the Schiff base and provides that its deproton-tion and reprotonation occur on different sides. The conformational change has characteristics typical for relaxations in proteins. In addition, it is shown that at 260 K an equilibrium siuts between the M and N forms.

Original languageEnglish
Pages (from-to)473-477
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume88
Issue number2
Publication statusPublished - 1991

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Schiff Bases
Protons
Proteins
Amides
Temperature

Keywords

  • Conformational relaxation

ASJC Scopus subject areas

  • General
  • Genetics

Cite this

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title = "Infrared spectroscopic demonstration of a conformational change in bacterorhodopsin involved in proton pumping",
abstract = "Infrared spectral changes in bacteriorhoapsin (bR) were followed during the slow decay of the M intermediate in the temperature region 240-260 K. The decay of the M form is characterized by the disappearance of the thylene bands and the bands indicating the reprotonation of the Schiff base. The route of Schiff-base reprotonation compeletely changes between 240 K and 260 K. At 240 K reprotontion occurs from Asp-85, the group to which the proton was released during M formation, and there is no pumping. At 260 the Schiff-base reprotonation takes place through Asp-96 from the cytoplasmic side, in the normal sequence assumed for proton pumping. The dramatic change in the route of Schiffase reprotonation is coupled to a protein conformational exchange characterized by the change of the ratio of the two amide I bands at 1658 cm-1 and 1669 cm-1. This conforma-tional change is interpreted as the conformational switch fracial for proton pumping: a protein relaxation following M conformatin results in a local rearrangement of the group, in the icinity of the Schiff base. The rearrangement changes the accesibility of the Schiff base and provides that its deproton-tion and reprotonation occur on different sides. The conformational change has characteristics typical for relaxations in proteins. In addition, it is shown that at 260 K an equilibrium siuts between the M and N forms.",
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T1 - Infrared spectroscopic demonstration of a conformational change in bacterorhodopsin involved in proton pumping

AU - Ormos, P.

PY - 1991

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N2 - Infrared spectral changes in bacteriorhoapsin (bR) were followed during the slow decay of the M intermediate in the temperature region 240-260 K. The decay of the M form is characterized by the disappearance of the thylene bands and the bands indicating the reprotonation of the Schiff base. The route of Schiff-base reprotonation compeletely changes between 240 K and 260 K. At 240 K reprotontion occurs from Asp-85, the group to which the proton was released during M formation, and there is no pumping. At 260 the Schiff-base reprotonation takes place through Asp-96 from the cytoplasmic side, in the normal sequence assumed for proton pumping. The dramatic change in the route of Schiffase reprotonation is coupled to a protein conformational exchange characterized by the change of the ratio of the two amide I bands at 1658 cm-1 and 1669 cm-1. This conforma-tional change is interpreted as the conformational switch fracial for proton pumping: a protein relaxation following M conformatin results in a local rearrangement of the group, in the icinity of the Schiff base. The rearrangement changes the accesibility of the Schiff base and provides that its deproton-tion and reprotonation occur on different sides. The conformational change has characteristics typical for relaxations in proteins. In addition, it is shown that at 260 K an equilibrium siuts between the M and N forms.

AB - Infrared spectral changes in bacteriorhoapsin (bR) were followed during the slow decay of the M intermediate in the temperature region 240-260 K. The decay of the M form is characterized by the disappearance of the thylene bands and the bands indicating the reprotonation of the Schiff base. The route of Schiff-base reprotonation compeletely changes between 240 K and 260 K. At 240 K reprotontion occurs from Asp-85, the group to which the proton was released during M formation, and there is no pumping. At 260 the Schiff-base reprotonation takes place through Asp-96 from the cytoplasmic side, in the normal sequence assumed for proton pumping. The dramatic change in the route of Schiffase reprotonation is coupled to a protein conformational exchange characterized by the change of the ratio of the two amide I bands at 1658 cm-1 and 1669 cm-1. This conforma-tional change is interpreted as the conformational switch fracial for proton pumping: a protein relaxation following M conformatin results in a local rearrangement of the group, in the icinity of the Schiff base. The rearrangement changes the accesibility of the Schiff base and provides that its deproton-tion and reprotonation occur on different sides. The conformational change has characteristics typical for relaxations in proteins. In addition, it is shown that at 260 K an equilibrium siuts between the M and N forms.

KW - Conformational relaxation

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