Charge motions during the photocycle of pharaonis halorhodopsin

Krisztina Ludmann, Grazyna Ibron, Janos K. Lanyi, G. Váró

Research output: Contribution to journalArticle

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Abstract

Oriented gel samples were prepared from halorhodopsin-containing membranes from Natronobacterium pharaonis, and their photoelectric responses to laser flash excitation were measured at different chloride concentrations. The fast component of the current signal displayed a characteristic dependency on chloride concentration, and could be interpreted as a sum of two signals that correspond to the responses at high-chloride and no- chloride, but high-sulfate, concentration. The chloride concentration- dependent transition between the two signals followed the titration curve determined earlier from spectroscopic titration. The voltage signal was very similar to that reported by another group (Kalaidzidis, I. V., Y. L. Kalaidzidis, and A. D. Kaulen. 1998. FEBS Lett. 427:59-63). The absorption kinetics, measured at four wavelengths, fit the kinetic model we had proposed earlier. The calculated time-dependent concentrations of the intermediates were used to fit the voltage signal. Although no negative electric signal was observed at high chloride concentration, the calculated electrogenicity of the K intermediate was negative, and very similar to that of bacteriorhodopsin. The late photocycle intermediates (O, HR', and HR) had almost equal electrogenicities, explaining why no chloride-dependent time constant was identified earlier by Kalaidzidis et al. The calculated electrogenicities, and the spectroscopic information for the chloride release and uptake steps of the photocycle, suggest a mechanism for the chloride- translocation process in this pump.

Original languageEnglish
Pages (from-to)959-966
Number of pages8
JournalBiophysical Journal
Volume78
Issue number2
Publication statusPublished - 2000

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Halorhodopsins
Chlorides
Natronobacterium
Bacteriorhodopsins
Sulfates
Lasers
Gels

ASJC Scopus subject areas

  • Biophysics

Cite this

Ludmann, K., Ibron, G., Lanyi, J. K., & Váró, G. (2000). Charge motions during the photocycle of pharaonis halorhodopsin. Biophysical Journal, 78(2), 959-966.

Charge motions during the photocycle of pharaonis halorhodopsin. / Ludmann, Krisztina; Ibron, Grazyna; Lanyi, Janos K.; Váró, G.

In: Biophysical Journal, Vol. 78, No. 2, 2000, p. 959-966.

Research output: Contribution to journalArticle

Ludmann, K, Ibron, G, Lanyi, JK & Váró, G 2000, 'Charge motions during the photocycle of pharaonis halorhodopsin', Biophysical Journal, vol. 78, no. 2, pp. 959-966.
Ludmann, Krisztina ; Ibron, Grazyna ; Lanyi, Janos K. ; Váró, G. / Charge motions during the photocycle of pharaonis halorhodopsin. In: Biophysical Journal. 2000 ; Vol. 78, No. 2. pp. 959-966.
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