TY - JOUR
T1 - Effect of lipid-protein interaction on the color of bacteriorhodopsin
AU - Pande, C.
AU - Callender, R.
AU - Baribeau, J.
AU - Boucher, F.
AU - Pande, A.
N1 - Funding Information:
This work was supported in part by a National Institutes of Health grant EYO 3142 (R.C.) and by Natural Sciences and Engineering Research Council of Canada (F.B.).
PY - 1989/2
Y1 - 1989/2
N2 - 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.
AB - 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.
KW - (Bacteriorhodopsin)
KW - Chromophore
KW - Lipid-protein interaction
KW - Opsin shift
KW - Protonated Schiff base
KW - Resonance Raman spectroscopy
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U2 - 10.1016/S0005-2728(89)80430-X
DO - 10.1016/S0005-2728(89)80430-X
M3 - Article
C2 - 2917159
AN - SCOPUS:0024979932
SN - 0005-2728
VL - 973
SP - 257
EP - 262
JO - BBA - Bioenergetics
JF - BBA - Bioenergetics
IS - 2
ER -