Protonation of a novel intermediate P is involved in the M → bR step of the bacteriorhodopsin photocycle

FEBS Letters

Zorina, V.V.¹  Drachev, L.A.¹  Kaulen, A.D.¹  Skulachev, V.P.¹ 

[1] Department of Bioenergetics, A.N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, Moscow 119899, USSR

关键词: Bacteriorhodopsin;    Photocycle;    Proton pump;    pH indicator;    Purple membrane (Halobacterium halobium);   

DOI  :  10.1016/0014-5793(86)81134-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

A novel intermediate (P) of the bacteriorhodopsin (bR) photocycle, appearing between M412 and bR is described. Like bR, intermediate P shows an absorption maximum at 560–570 nm. However, the extinction coefficient of P is somewhat lower than that of bR. Moreover, there are some differences in spectra of bR and P at wavelengths shorter than 450 nm. The P → bR transition correlates with the absorption of H⁺ from the water medium. The following conditions proved to be favourable for the detection of the new intermediate: a high salt concentration, low light intensity and low temperature (0.5°C). The P → bR transition is strongly decelerated by a small amount of Triton X-100. Illumination of P does not produce M412 before bR is formed. It is assumed that M412 converts to P when the Schiff base is protonated by a proton transferred from a protein protolytic group which participates in the inward H⁺-conductivity pathway. Reprotonation of this group results in the conversion of P to bR. No more than 1 H⁺ is transported per bR photocycle.

【 授权许可】

Unknown