Pathways of proton release in the bacteriorhodopsin photocycle

L. Zimányi, G. Váró, Man Chang, Baofu Ni, Richard Needleman, Janos K. Lanyi

Research output: Contribution to journalArticle

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Abstract

The pH dependencies of the rate constants in the photocycles of recombinant D96N and D115N/ D96N bacteriorhodopsins were determined from time-resolved difference spectra between 70 ns and 420 ms after photoexcitation. The results were consistent with the model suggested earlier for proteins containing D96N substitution: BR →hv K ↔ L ↔ M1 ↔ M2 ↔ BR. Only the M2 → M1 back-reaction was pH-dependent: its rate increased with increasing [H+] between pH 5 and 8. We conclude from quantitative analysis of this pH dependency that its reverse, the M1 → M2 reaction, is linked to the release of a proton from a group with a pKa = 5.8. This suggests a model for wild-type bacteriorhodopsin in which at pH > 5.8 the transported proton is released on the extracellular side from this as yet unknown group and on the 100-μs time scale, but at pH 6, proton release preceded proton uptake, but at pH 1 → M2 reaction includes a second kinetic step in addition to proton release; this is probably the earlier postulated extracellular-to-cytoplasmic reorientation switch in the proton pump.

Original languageEnglish
Pages (from-to)8535-8543
Number of pages9
JournalBiochemistry
Volume31
Issue number36
Publication statusPublished - 1992

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Bacteriorhodopsins
Protons
Proton Pumps
Photoexcitation
Rate constants
Substitution reactions
Switches
Kinetics
Chemical analysis
Proteins

ASJC Scopus subject areas

  • Biochemistry

Cite this

Zimányi, L., Váró, G., Chang, M., Ni, B., Needleman, R., & Lanyi, J. K. (1992). Pathways of proton release in the bacteriorhodopsin photocycle. Biochemistry, 31(36), 8535-8543.

Pathways of proton release in the bacteriorhodopsin photocycle. / Zimányi, L.; Váró, G.; Chang, Man; Ni, Baofu; Needleman, Richard; Lanyi, Janos K.

In: Biochemistry, Vol. 31, No. 36, 1992, p. 8535-8543.

Research output: Contribution to journalArticle

Zimányi, L, Váró, G, Chang, M, Ni, B, Needleman, R & Lanyi, JK 1992, 'Pathways of proton release in the bacteriorhodopsin photocycle', Biochemistry, vol. 31, no. 36, pp. 8535-8543.
Zimányi L, Váró G, Chang M, Ni B, Needleman R, Lanyi JK. Pathways of proton release in the bacteriorhodopsin photocycle. Biochemistry. 1992;31(36):8535-8543.
Zimányi, L. ; Váró, G. ; Chang, Man ; Ni, Baofu ; Needleman, Richard ; Lanyi, Janos K. / Pathways of proton release in the bacteriorhodopsin photocycle. In: Biochemistry. 1992 ; Vol. 31, No. 36. pp. 8535-8543.
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