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Accession number;02A0304398
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| Title;Effect of Metal Ion Exchange on Bacteriorhodopsin Proton Pump. |
| Author;
NUGA TAKAHIKO
(Inst. Ind. Sci., Univ. Tokyo)
SAGA YOSHITAKA
(Ritsumeikan Univ., Fac. of Sci. and Eng.)
YOSHIDA SHOICHIRO
(Inst. Ind. Sci., Univ. Tokyo)
WATANABE TADASHI
(Inst. Ind. Sci., Univ. Tokyo)
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Journal Title;Abstracts. Symposium on Biofunctional Chemistry
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Journal Code:L0836A
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ISSN:
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VOL.16th;NO.;PAGE.84-85(2001)
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| Figure&Table&Reference; |
| Pub. Country;Japan |
| Language;Japanese |
| Abstract;Bacteriorhodopsin(bR), the retinal-containing protein in the purple membrane of Halobacterium salinarium, functions as a light-driven proton pump. bR is normally purple, and turns blue by removal of metal ions. Metal ions bound to bR molecules can be easily exchanged by passage through a cation exchange colume and addition of desired cations. The effect of metal ion exchange on bR proton pump was investigated by means of spectroscopic and photoelectrochemical measurements. The pH-profiles of the rate of bR dark-adaptation was dependent on the bound metal ions. From the curves, we estimated the pKa of a proton release group of metal-substituted bRs. The pKa of the proton release group shifted to lower pH with an increase in the cation valency. The photocurrent measurement of metal-substituted bRs also showed a similar pKa shift of the proton-releasing group. These results suggest that bound metal ions affect the pKa of the proton-releasing group on the extracellular surface of bR molcules. (author abst.) |
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