Isolation and characterization of proteorhodopsin homologue from Yellow Sea of Korea

초록

Many organisms use proton pump to earn energy for living. Some proton pumps start to work by light and one of the famous proteins are called proteorhodopsin (PR). From recent study it used not only protons but also mono-valent cations, divalent cations, or mono-valent anions during pumping activity. The goal of this study is to find new types of proton pumping proteins in the surface of the ocean. Metagenome samples were collected from the beach in Taean-gun and Incheon (Kkotji beach (36A degrees 30'0''N, 126A degrees 19'56''E), Kkotji mud (36A degrees 30'8''N, 126A degrees 19'60''E), Duegi beach (36A degrees 31'6''N, 126A degrees 19'39''E), Sorae salt pond (37A degrees 24'25''N, 126A degrees 44'41''E), swamp (37A degrees 24'59''N, 126A degrees 44'54''E) and reservoir (37A degrees 24'39''N, 126A degrees 45'5''E) in West Sea of Korea. Genomic DNA of each sample was isolated and used for PCR with specific primers for PR and sodium pumping rhodopsin. As a result, we obtained an unidentified PR in Duegi beach sample. The unidentified PR was expressed with chimeric expression system. It has 528 nm absorption maximum at pH 7. By the light differential spectrum measurement, putative M and O photo-intermediates were detected at around 400 and 600 nm, respectively. Similar to GPR, it has light driven outward proton transfer activity.

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