Proteorhodopsin from Dokdonia sp. PRO95 is a light-driven Na+-pump

Area of Science:

• Biochemistry
• Molecular Biology
• Microbiology

Background:

• Proteorhodopsins are light-activated ion pumps found in bacteria.
• Understanding their transport mechanisms is crucial for bioenergetics and biotechnology.

Purpose of the Study:

• To clone and express the proteorhodopsin gene from Dokdonia sp. PRO95 in E. coli.
• To characterize the ion transport activity of the expressed proteorhodopsin.
• To evaluate its potential as a model system for studying sodium transport.

Main Methods:

• Gene cloning and heterologous expression in Escherichia coli.
• Spectrophotometric analysis of media pH changes upon illumination.
• Investigation of ion transport using specific ion substitutions and chemical modifiers (CCCP, SCN-).

Main Results:

• Illumination of E. coli expressing Dokdonia sp. PRO95 proteorhodopsin caused media alkalinization in Na+-containing buffer, indicating Na+ uptake.
• The transport was sensitive to CCCP and SCN-, consistent with ion pumping.
• In Na+-free (K+-substituted) media, illumination led to acidification, further supporting Na+ export.
• CCCP-resistant transmembrane sodium export was observed.

Conclusions:

• Proteorhodopsin AEX55013 from Dokdonia sp. PRO95 functions as a primary light-driven sodium (Na+) pump.
• High-level heterologous production, stability, and purity make it a valuable model for studying active sodium translocation mechanisms.