Effect of lipid-protein interaction on the color of bacteriorhodopsin

C. Pande, R. Callender, J. Baribeau, F. Boucher, A. Pande

Research output: Contribution to journalArticle

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Abstract

Detergent solubilization and subsequent delipidation of bacteriorhodopsin (bR) results in the formation of a newspecies absorbing maximally at 480 nm (bR480). Upon lowering the pH, its absorption shifts to 540 nm (bR540). The pK of this equilibrium is 2.6, with the higher pH favoring bR 480 (Baribeau, J. and Boucher, F. (1987) Biochim. Biophysica Acta, 890, 275-278). Resonance Raman spectroscopy shows that bR480, like the native bR, contains a protonated Schiff base (PSB) linkage between the chromophore and the protein. However, the Schiff base vibrational frequency in bR480, and its shift upon deuteration, are quite different from these in the native bR, suggesting changes in the Schiff base environment upon delipidation. Infrared absorption and circular-dichroism (CD) spectral studies do not show any net change in the protein secondary structure upon formation of bR480. It is shown that deprotonation of the Schiff base is not the only mechanism of producing hypsochromic shift in the absorption maximum of bR-derived pigments, subtle changes in the protein tertiary structure, affecting the Schiff base environment of the chromophore, may play an equally significant role in the color regulation of bR-derived pigments.

Original languageEnglish (US)
Pages (from-to)257-262
Number of pages6
JournalBBA - Bioenergetics
Volume973
Issue number2
DOIs
StatePublished - Feb 1989

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Keywords

  • (Bacteriorhodopsin)
  • Chromophore
  • Lipid-protein interaction
  • Opsin shift
  • Protonated Schiff base
  • Resonance Raman spectroscopy

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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