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Reconstitution of Aquaporin Z and Bacteriorhodopsin in artificial membrane for water purification
Aquaporin Z and bacteriorhodopsin known as membrane protein transport water molecules and protons, respectively, in and out of the cell in highly selective manner. The selective character of these biomolecules can be applied to water filtration or other industry. However, transmembrane protein like as aquaporin Z and bacteriorhodopsin has many problems for using associated with expression, purification, and activation of protein character. To solve these problems, we developed purification system and characterization method for transmembrane protein. Green Fluorescence Protein (GFP)-fused aquaporin Z were expressed in inducible expression vector system, and purified by Ni-NTA affinity chromatography. GFP-fused aquaporin Z proteins were incorporated into the liposome for optical observation of water flux, and tested in hypertonic external condition by osmotic pressure to check water molecule selective transport. Bacteriorhodopsin was acquired by same method for aquaporin Z purification, but need to activation process by retinal cofactor because Escherichia coli has not retinal synthesis system. According to the absorbance spectra analysis, we confirmed that the purified bacteriorhodopsin was activated by retinal. This study will help to understanding of aquaporin Z and bacteriorhodopsin character and industrial application of transmembrane protein.
