Structural changes of pharaonis phoborhodopsin upon photoisomerization of the retinal chromophore: Infrared spectral comparison with bacteriorhodopsin

H. Kandori, K. Shimono, Yuki Sudo, M. Iwamoto, Y. Shichida, N. Kamo

Research output: Contribution to journalArticle

99 Citations (Scopus)

Abstract

Archaeal rhodopsins possess a retinal molecule as their chromophores, and their light energy and light signal conversions are triggered by all-trans to 13-cis isomerization of the retinal chromophore. Relaxation through structural changes of the protein then leads to functional processes, proton pump in bacteriorhodopsin and transducer activation in sensory rhodopsins. In the present paper, low-temperature Fourier transform infrared spectroscopy is applied to phoborhodopsin from Natronobacterium pharaonis (ppR), a photoreceptor for the negative phototaxis of the bacteria, and infrared spectral changes before and after photoisomerization are compared with those of bacteriorhodopsin (BR) at 77 K. Spectral comparison of the C-C stretching vibrations of the retinal chromophore shows that chromophore conformation of the polyene chain is similar between ppR and BR. This fact implies that the unique chromophore-protein interaction in ppR, such as the blue-shifted absorption spectrum with vibrational fine structure, originates from both ends, the β-ionone ring and the Schiff base regions. In fact, less planer ring structure and stronger hydrogen bond of the Schiff base were suggested for ppR. Similar frequency changes upon photoisomerization are observed for the C=N stretch of the retinal Schiff base and the stretch of the neighboring threonine side chain (Thr79 in ppR and Thr89 in BR), suggesting that photoisomerization in ppR is driven by the motion of the Schiff base like BR. Nevertheless, the structure of the K state after photoisomerization is different between ppR and BR, In BR, chromophore distortion is localized in the Schiff base region, as shown in its hydrogen out-of-plane vibrations. In contrast, more extended structural changes take place in ppR in view of chromophore distortion and protein structural changes. Such structure of the K intermediate of ppR is probably correlated with its high thermal stability. In fact, almost identical infrared spectra are obtained between 77 and 170 K in ppR. Unique chromophore-protein interaction and photoisomerization processes in ppR are discussed on the basis of the present infrared spectral comparison with BR.

Original languageEnglish
Pages (from-to)9238-9246
Number of pages9
JournalBiochemistry
Volume40
Issue number31
DOIs
Publication statusPublished - Aug 7 2001
Externally publishedYes

Fingerprint

Bacteriorhodopsins
Photoisomerization
Chromophores
Schiff Bases
Infrared radiation
Vibration
Natronobacterium
Microbial Rhodopsins
Hydrogen
Sensory Rhodopsins
Proteins
Norisoprenoids
Polyenes
Light
Proton Pumps
Fourier Transform Infrared Spectroscopy
Threonine
Isomerization
Transducers
Stretching

ASJC Scopus subject areas

  • Biochemistry

Cite this

Structural changes of pharaonis phoborhodopsin upon photoisomerization of the retinal chromophore : Infrared spectral comparison with bacteriorhodopsin. / Kandori, H.; Shimono, K.; Sudo, Yuki; Iwamoto, M.; Shichida, Y.; Kamo, N.

In: Biochemistry, Vol. 40, No. 31, 07.08.2001, p. 9238-9246.

Research output: Contribution to journalArticle

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T1 - Structural changes of pharaonis phoborhodopsin upon photoisomerization of the retinal chromophore

T2 - Infrared spectral comparison with bacteriorhodopsin

AU - Kandori, H.

AU - Shimono, K.

AU - Sudo, Yuki

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AU - Shichida, Y.

AU - Kamo, N.

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N2 - Archaeal rhodopsins possess a retinal molecule as their chromophores, and their light energy and light signal conversions are triggered by all-trans to 13-cis isomerization of the retinal chromophore. Relaxation through structural changes of the protein then leads to functional processes, proton pump in bacteriorhodopsin and transducer activation in sensory rhodopsins. In the present paper, low-temperature Fourier transform infrared spectroscopy is applied to phoborhodopsin from Natronobacterium pharaonis (ppR), a photoreceptor for the negative phototaxis of the bacteria, and infrared spectral changes before and after photoisomerization are compared with those of bacteriorhodopsin (BR) at 77 K. Spectral comparison of the C-C stretching vibrations of the retinal chromophore shows that chromophore conformation of the polyene chain is similar between ppR and BR. This fact implies that the unique chromophore-protein interaction in ppR, such as the blue-shifted absorption spectrum with vibrational fine structure, originates from both ends, the β-ionone ring and the Schiff base regions. In fact, less planer ring structure and stronger hydrogen bond of the Schiff base were suggested for ppR. Similar frequency changes upon photoisomerization are observed for the C=N stretch of the retinal Schiff base and the stretch of the neighboring threonine side chain (Thr79 in ppR and Thr89 in BR), suggesting that photoisomerization in ppR is driven by the motion of the Schiff base like BR. Nevertheless, the structure of the K state after photoisomerization is different between ppR and BR, In BR, chromophore distortion is localized in the Schiff base region, as shown in its hydrogen out-of-plane vibrations. In contrast, more extended structural changes take place in ppR in view of chromophore distortion and protein structural changes. Such structure of the K intermediate of ppR is probably correlated with its high thermal stability. In fact, almost identical infrared spectra are obtained between 77 and 170 K in ppR. Unique chromophore-protein interaction and photoisomerization processes in ppR are discussed on the basis of the present infrared spectral comparison with BR.

AB - Archaeal rhodopsins possess a retinal molecule as their chromophores, and their light energy and light signal conversions are triggered by all-trans to 13-cis isomerization of the retinal chromophore. Relaxation through structural changes of the protein then leads to functional processes, proton pump in bacteriorhodopsin and transducer activation in sensory rhodopsins. In the present paper, low-temperature Fourier transform infrared spectroscopy is applied to phoborhodopsin from Natronobacterium pharaonis (ppR), a photoreceptor for the negative phototaxis of the bacteria, and infrared spectral changes before and after photoisomerization are compared with those of bacteriorhodopsin (BR) at 77 K. Spectral comparison of the C-C stretching vibrations of the retinal chromophore shows that chromophore conformation of the polyene chain is similar between ppR and BR. This fact implies that the unique chromophore-protein interaction in ppR, such as the blue-shifted absorption spectrum with vibrational fine structure, originates from both ends, the β-ionone ring and the Schiff base regions. In fact, less planer ring structure and stronger hydrogen bond of the Schiff base were suggested for ppR. Similar frequency changes upon photoisomerization are observed for the C=N stretch of the retinal Schiff base and the stretch of the neighboring threonine side chain (Thr79 in ppR and Thr89 in BR), suggesting that photoisomerization in ppR is driven by the motion of the Schiff base like BR. Nevertheless, the structure of the K state after photoisomerization is different between ppR and BR, In BR, chromophore distortion is localized in the Schiff base region, as shown in its hydrogen out-of-plane vibrations. In contrast, more extended structural changes take place in ppR in view of chromophore distortion and protein structural changes. Such structure of the K intermediate of ppR is probably correlated with its high thermal stability. In fact, almost identical infrared spectra are obtained between 77 and 170 K in ppR. Unique chromophore-protein interaction and photoisomerization processes in ppR are discussed on the basis of the present infrared spectral comparison with BR.

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