Proton transfer from Asp-96 to the bacteriorhodopsin schiff base is caused by a decrease of the pKa of Asp-96 which follows a protein backbone conformational change

Yi Cao, György Váró, G. Váró, Daniel M. Czajkowsky, Mark S. Braiman, Richard Needleman, Janos K. Lanyi

Research output: Contribution to journalArticle

88 Citations (Scopus)

Abstract

In the bacteriorhodopsin photocycle the transported proton crosses the major part of the hydrophobic barrier during the M to N reaction; in this step the Schiff base near the middle of the protein is reprotonated from D96 located near the cytoplasmic surface. In the recombinant D212N protein at pH >6, the Schiff base remains protonated throughout the photocycle [Needleman, Chang, Ni, Váró, Fornés, White, & Lanyi (1991) J. Biol. Chem. 266, 11478-11484]. Time-resolved difference spectra in the visible and infrared are described by the kinetic scheme BR →hv K ↔ L ↔ N (→N′) →BR. As evidenced by the large negative 1742-cm-1 band of the COOH group of the carboxylic acid, deprotonation of D96 in the N state takes place in spite of the absence of the unprotonated Schiff base acceptor group of the M intermediate. Instead of internal proton transfer to the Schiff base, the proton is released to the bulk, and can be detected with the indicator dye pyranine during the accumulation of N′. The D212N/D96N protein has a similar photocycle, but no proton is released. As in wild-type, deprotonation of D96 in the N state is accompanied by a protein backbone conformational change indicated by characteristic amide I and II bands. In D212N the residue D96 can thus deprotonate independent of the Schiff base, but perhaps dependent on the detected protein conformational change. This could occur through increased charge interaction between D96 and R227 and/or increased hydration near D96. We suggest that the proton transfer from D96 to the Schiff base in the wild-type photocycle is driven also by such a decrease in the pKa of D96.

Original languageEnglish
Pages (from-to)1981-1990
Number of pages10
JournalBiochemistry
Volume32
Issue number8
Publication statusPublished - 1993

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Bacteriorhodopsins
Proton transfer
Schiff Bases
Protons
Deprotonation
Proteins
Carboxylic Acids
Recombinant Proteins
Amides
Hydration
Coloring Agents
Infrared radiation
Kinetics

ASJC Scopus subject areas

  • Biochemistry

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Proton transfer from Asp-96 to the bacteriorhodopsin schiff base is caused by a decrease of the pKa of Asp-96 which follows a protein backbone conformational change. / Cao, Yi; Váró, György; Váró, G.; Czajkowsky, Daniel M.; Braiman, Mark S.; Needleman, Richard; Lanyi, Janos K.

In: Biochemistry, Vol. 32, No. 8, 1993, p. 1981-1990.

Research output: Contribution to journalArticle

Cao, Yi ; Váró, György ; Váró, G. ; Czajkowsky, Daniel M. ; Braiman, Mark S. ; Needleman, Richard ; Lanyi, Janos K. / Proton transfer from Asp-96 to the bacteriorhodopsin schiff base is caused by a decrease of the pKa of Asp-96 which follows a protein backbone conformational change. In: Biochemistry. 1993 ; Vol. 32, No. 8. pp. 1981-1990.
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abstract = "In the bacteriorhodopsin photocycle the transported proton crosses the major part of the hydrophobic barrier during the M to N reaction; in this step the Schiff base near the middle of the protein is reprotonated from D96 located near the cytoplasmic surface. In the recombinant D212N protein at pH >6, the Schiff base remains protonated throughout the photocycle [Needleman, Chang, Ni, V{\'a}r{\'o}, Forn{\'e}s, White, & Lanyi (1991) J. Biol. Chem. 266, 11478-11484]. Time-resolved difference spectra in the visible and infrared are described by the kinetic scheme BR →hv K ↔ L ↔ N (→N′) →BR. As evidenced by the large negative 1742-cm-1 band of the COOH group of the carboxylic acid, deprotonation of D96 in the N state takes place in spite of the absence of the unprotonated Schiff base acceptor group of the M intermediate. Instead of internal proton transfer to the Schiff base, the proton is released to the bulk, and can be detected with the indicator dye pyranine during the accumulation of N′. The D212N/D96N protein has a similar photocycle, but no proton is released. As in wild-type, deprotonation of D96 in the N state is accompanied by a protein backbone conformational change indicated by characteristic amide I and II bands. In D212N the residue D96 can thus deprotonate independent of the Schiff base, but perhaps dependent on the detected protein conformational change. This could occur through increased charge interaction between D96 and R227 and/or increased hydration near D96. We suggest that the proton transfer from D96 to the Schiff base in the wild-type photocycle is driven also by such a decrease in the pKa of D96.",
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T1 - Proton transfer from Asp-96 to the bacteriorhodopsin schiff base is caused by a decrease of the pKa of Asp-96 which follows a protein backbone conformational change

AU - Cao, Yi

AU - Váró, György

AU - Váró, G.

AU - Czajkowsky, Daniel M.

AU - Braiman, Mark S.

AU - Needleman, Richard

AU - Lanyi, Janos K.

PY - 1993

Y1 - 1993

N2 - In the bacteriorhodopsin photocycle the transported proton crosses the major part of the hydrophobic barrier during the M to N reaction; in this step the Schiff base near the middle of the protein is reprotonated from D96 located near the cytoplasmic surface. In the recombinant D212N protein at pH >6, the Schiff base remains protonated throughout the photocycle [Needleman, Chang, Ni, Váró, Fornés, White, & Lanyi (1991) J. Biol. Chem. 266, 11478-11484]. Time-resolved difference spectra in the visible and infrared are described by the kinetic scheme BR →hv K ↔ L ↔ N (→N′) →BR. As evidenced by the large negative 1742-cm-1 band of the COOH group of the carboxylic acid, deprotonation of D96 in the N state takes place in spite of the absence of the unprotonated Schiff base acceptor group of the M intermediate. Instead of internal proton transfer to the Schiff base, the proton is released to the bulk, and can be detected with the indicator dye pyranine during the accumulation of N′. The D212N/D96N protein has a similar photocycle, but no proton is released. As in wild-type, deprotonation of D96 in the N state is accompanied by a protein backbone conformational change indicated by characteristic amide I and II bands. In D212N the residue D96 can thus deprotonate independent of the Schiff base, but perhaps dependent on the detected protein conformational change. This could occur through increased charge interaction between D96 and R227 and/or increased hydration near D96. We suggest that the proton transfer from D96 to the Schiff base in the wild-type photocycle is driven also by such a decrease in the pKa of D96.

AB - In the bacteriorhodopsin photocycle the transported proton crosses the major part of the hydrophobic barrier during the M to N reaction; in this step the Schiff base near the middle of the protein is reprotonated from D96 located near the cytoplasmic surface. In the recombinant D212N protein at pH >6, the Schiff base remains protonated throughout the photocycle [Needleman, Chang, Ni, Váró, Fornés, White, & Lanyi (1991) J. Biol. Chem. 266, 11478-11484]. Time-resolved difference spectra in the visible and infrared are described by the kinetic scheme BR →hv K ↔ L ↔ N (→N′) →BR. As evidenced by the large negative 1742-cm-1 band of the COOH group of the carboxylic acid, deprotonation of D96 in the N state takes place in spite of the absence of the unprotonated Schiff base acceptor group of the M intermediate. Instead of internal proton transfer to the Schiff base, the proton is released to the bulk, and can be detected with the indicator dye pyranine during the accumulation of N′. The D212N/D96N protein has a similar photocycle, but no proton is released. As in wild-type, deprotonation of D96 in the N state is accompanied by a protein backbone conformational change indicated by characteristic amide I and II bands. In D212N the residue D96 can thus deprotonate independent of the Schiff base, but perhaps dependent on the detected protein conformational change. This could occur through increased charge interaction between D96 and R227 and/or increased hydration near D96. We suggest that the proton transfer from D96 to the Schiff base in the wild-type photocycle is driven also by such a decrease in the pKa of D96.

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VL - 32

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JO - Biochemistry

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SN - 0006-2960

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