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FEBS Lett. 2010 Oct 8;584(19):4193-6. doi: 10.1016/j.febslet.2010.09.005. Epub 2010 Sep 8.

Predicted bacteriorhodopsin from Exiguobacterium sibiricum is a functional proton pump.

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Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russian Federation.


The predicted Exigobacterium sibiricum bacterirhodopsin gene was amplified from an ancient Siberian permafrost sample. The protein bacteriorhodopsin from Exiguobacterium sibiricum (ESR) encoded by this gene was expressed in Escherichia coli membrane. ESR bound all-trans-retinal and displayed an absorbance maximum at 534nm without dark adaptation. The ESR photocycle is characterized by fast formation of an M intermediate and the presence of a significant amount of an O intermediate. Proteoliposomes with ESR incorporated transport protons in an outward direction leading to medium acidification. Proton uptake at the cytoplasmic surface of these organelles precedes proton release and coincides with M decay/O rise of the ESR.

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