RESONANCE RAMAN STUDIES OF BACTERIORHODOPSIN ANALOGUES

Abstract— We present the results of resonance Raman measurements on a series of bacteriorhodopsin (bR) analogues formed from synthetic retinals which have replaced the native chromophore in the active site. Specifically, 5,6‐dihydro‐bR, 13‐desmethyl‐bR, 10‐methyl‐bR, 14‐methyl‐bR, and 10.14‐dimethyl‐bR have been studied. All five analogues bind and form Schiff base retinal‐apoprotein linkages. While the Schiff base linkages of 5,6‐dihydro‐bR, 13‐desmethyl‐bR, and 10‐methyl‐bR are protonated, like the native chromophore, the 14‐methyl‐bR, and 10,14‐dimethyl‐bR Schiff bases are unprotonated. These results suggest that the binding site of bacteriorhodopsin near the Schiff base moiety is different from that of rhodopsin. The protonated Schiff base ‐C=NH‐ stretching frequency of 5.6‐dihydro‐bR lies at 1660 cm‐1 which is unusually high for a bacteriorhodopsin based pigment. The downward shift upon deuteration is 16 cm‐1, essentially identical to that measured for bacteriorhodopsin. This and the other analogue results strongly reinforce our previous arguments that the Schiff base stretching frequency is determined in large part by two factors, the C=N force constant and the stretch interaction with C=N‐H bend. On the other hand, the deuterium isotope effect is determined primarily by the stretch‐bend interaction.

[1]  B. Honig,et al.  Stability of "salt bridges" in membrane proteins. , 1984, Proceedings of the National Academy of Sciences of the United States of America.

[2]  S. O. Smith,et al.  Determination of retinal Schiff base configuration in bacteriorhodopsin. , 1984, Proceedings of the National Academy of Sciences of the United States of America.

[3]  S. O. Smith,et al.  Dark-adapted bacteriorhodopsin contains 13-cis, 15-syn and all-trans, 15-anti retinal Schiff bases. , 1984, Proceedings of the National Academy of Sciences of the United States of America.

[4]  B. Honig,et al.  Correlation of vibrational frequencies with absorption maxima in polyenes, rhodopsin, bacteriorhodopsin, and retinal analogs , 1983 .

[5]  R. Mathies,et al.  Vibrational analysis of all-trans-retinal , 1982 .

[6]  R. Callender,et al.  Resonance Raman study of the primary photochemistry of bacteriorhodopsin. , 1981, Proceedings of the National Academy of Sciences of the United States of America.

[7]  K. Nakanishi,et al.  Photochemical and functional properties of bacteriorhodopsins formed from 5,6-dihydro- and 5,6-dihydrodesmethylretinals. , 1981, Biochemistry.

[8]  B. Honig,et al.  An external point-charge model for bacteriorhodopsin to account for its purple color , 1980 .

[9]  K. Nakanishi,et al.  HYDRORETINALS AND HYDRORHODOPSINS , 1979 .

[10]  Michael G. Motto,et al.  An external point-charge model for wavelength regulation in visual pigments , 1979 .

[11]  R. Callender,et al.  Resonance Raman study of the dark-adapted form of the purple membrane protein. , 1979, Biochimica et biophysica acta.

[12]  T. Ebrey,et al.  The blue membrane: the 3-dehydroretinal-based artificial pigment of the purple membrane. , 1978, Biochemistry.

[13]  J. West,et al.  Photochemical synthesis of cis isomers of retinal analogs. 13-dehethylretinal. , 1978 .

[14]  K. Ohno,et al.  Effect of light-adaptation on the photoreaction of bacteriorhodopsin from Halobacterium halobium. , 1977, Biochimica et biophysica acta.

[15]  R. Callender.  Resonance Raman studies of visual pigments. , 1977, Annual review of biophysics and bioengineering.

[16]  B. Honig,et al.  Properties of several sterically modified retinal analogs and their photosensitive pigments , 1975 .

[17]  A. Oseroff,et al.  Resonance Raman spectroscopy of rhodopsin in retinal disk membranes. , 1974, Biochemistry.

[18]  Y. Hirose,et al.  Themal isomerisation between (−)-δ-elemenol and (+)-epi-δ elemenol , 1969 .

[19]  H. Huisman,et al.  Vitamin A analogues. V. Synthesis of 9-, 13-, and 9,13- desmethyl homologues of vitamin A. , 1966, Tetrahedron.