Time-Resolved Measurements of Photovoltage Generation by Bacteriorhodopsin and Halorhodopsin Adsorbed on a Thin Polymer Film

• Published in: Journal of biochemistry (Tokyo) Vol. 125; no. 2; pp. 270 - 276
• Main Authors: Muneyuki, Eiro, Shibazaki, Chie, Ohtan, Hiroyuki, Okuno, Daichi, Asaumi, Makoto, Mogi, Tatsushi
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.02.1999
• Subjects: bacteriorhodopsin; Bacteriorhodopsins - chemistry; halobacteria; Halobacterium - chemistry; Halobacterium salinarium; halorhodopsin; Halorhodopsins; Kinetics; Motion Pictures; Natronobacterium - chemistry; Natronobacterium pharaonis; Photochemistry - methods; photocycle; photovoltage; Polymers - chemistry; Time Factors
• ISSN: 0021-924X
• DOI: 10.1093/oxfordjournals.jbchem.a022283

We constructed a time-resolved photovoltage measurement system and examined the photovoltage kinetics of wild-type bacteriorhodopsin, its D96N mutant, and halorhodopsins from Halobacterium salinarum and Natronobacterium pharaonis. Upon illumination with a laser flash, wild-type bacteriorhodopsin showed photovoltage generation with fast (10–100 μs range) and slow (ms range) components while D96N lacked the latter, as reported previously [Holz, M., Drachev, L.A., Mogi, T., Otto, H., Kaulen, A.D., Heyn, M.P., Skulachev, V.P., and Khorana, H.G. (1989) Proc. Natl. Acad. Sci. USA 86, 2167–2171]. In contrast, photovoltage generation in halorhodopsins from H. salinarum and N. pharaonis was significant only in the ms time range. On the basis of the photovoltage kinetics and photocycle, we conclude that major charge (chloride) movements within halorhodopsin occur during the formation and decay of the N intermediate in the ms range. These observations are discussed in terms of the “Energization- Relaxation Channel Model” [Muneyuki, E., Ikematsu, M., and Yoshida, M. (1996) J. Phys. Chem. 100, 19687–19691].