Analogies between halorhodopsin and bacteriorhodopsin

Research output: Contribution to journalArticle

92 Citations (Scopus)

Abstract

The light-activated proton-pumping bacteriorhodopsin and chloride ion- pumping halorhodopsin are compared. They belong to the family of retinal proteins, with 25% amino acid sequence homology. Both proteins have seven α helices across the membrane, surrounding the retinal binding pocket. Photoexcitation of all-trans retinal leads to ion transporting photocycles, which exhibit great similarities in the two proteins, despite the differences in the ion transported. The spectra of the K, L, N and O intermediates, calculated using time-resolved spectroscopic measurements, are very similar in both proteins. The absorption kinetic measurements reveal that the chloride ion transporting photocycle of halorhodopsin does not have intermediate M characteristic for deprotonated Schiff base, and intermediate L dominates the process. Energetically the photocycle of bacteriorhodopsin is driven mostly by the decrease of the entropic energy, while the photocycle of halorhodopsin is enthalpy-driven. The ion transporting steps were characterized by the electrogenicity of the intermediates, calculated from the photoinduced transient electric signal measurements. The function of both proteins could be described with the 'local access' model developed for bacteriorhodopsin. In the framework of this model it is easy to understand how bacteriorhodopsin can be converted into a chloride pump, and halorhodopsin into a proton pump, by changing the ion specificity with added ions or site-directed mutagenesis. (C) 2000 Elsevier Science B.V.

Original languageEnglish
Pages (from-to)220-229
Number of pages10
JournalBBA - Bioenergetics
Volume1460
Issue number1
DOIs
Publication statusPublished - Aug 30 2000

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Halorhodopsins
Bacteriorhodopsins
Ions
Chlorides
Proteins
Proton Pumps
Amino Acid Sequence Homology
Mutagenesis
Schiff Bases
Photoexcitation
Site-Directed Mutagenesis
Protons
Enthalpy
Pumps
Membranes
Light
Amino Acids
Kinetics

Keywords

  • Bacteriorhodopsin
  • Chloride pump
  • Halorhodopsin
  • Photocycle
  • Proton pump
  • Retinal protein

ASJC Scopus subject areas

  • Biophysics

Cite this

Analogies between halorhodopsin and bacteriorhodopsin. / Váró, G.

In: BBA - Bioenergetics, Vol. 1460, No. 1, 30.08.2000, p. 220-229.

Research output: Contribution to journalArticle

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