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어떻게 생명체가 빛을 감지하는가 ?
연구주제: 로돕신의 광인지 및 광에너지 변환 기작의 규명
연구재료: 각 생명체에 존재하는 로돕신의 기능 및 생화학, 생물리학적 성질 연구
1. 고세균 (Archaea: Halobacterium, Natronomonas, Haloferax)
2. 박테리아 (Anabaena, Gloeobacter, Proteobacteria)
3. 진핵생물 (1) Algae: Chlamydomonas, Acetabularia, Guillardia, Pyrocyctis
(2) Fungi: Neurospora, Leptosphaeria
(3) Human: Melanopsin
연구내용
1. 세포내의 기능을 연구하기 위한 Knock-out 및 RNA interference
2. 막단백질의 대량발현, 분리 정제
3. 신호전달 단백질의 상호작용연구 (phosphorylation, gel shift assay등)
4. 광화학작분석 (spectrophotometer)
5 생물리학적분석 (Laser Flash photolysis, FTIR, Raman, solid-state NMR 공동연구)
6. 광변환 기작을 이용한 광바이오센서 제작
연구배경
로돕신 연구분야는 녹색광 수용체인 로돕신에 의한 광감지 조절 현상이 20세기 초에 발견된 이후로 고세균
(Archaea, 아케아)의 광주성 규명을 위한 순수 학문연구로서 연구되어져 왔고, 21세기 들어 proteorhodopsin의 발견으로 해양미생물의 태양에너지 이용 및 환경 적응성을 위한 실용적 응용을 목표로 다양한 연구들이 활발히 이루어져 왔다. 이 연구분야의 연구성과물이 Nature, Science, PNAS, PLoS Biology 등 유수한 저널에 게재되고 있으며, 에너지 전환기작의 이해에서 출발한 광감지 센서 등을 제작하는 공학분야에까지 응용이 되고 있다.
Microorganisms have evolved efficient photoenergy converters and sensitive photodetectors that monitor
spatial and temporal variation in light intensity and color. How do microbes sense the light?
Rhodopsins are diverse and relatively well characterized signal processing photoreceptors. The long-term objective of my research is to elucidate the molecular mechanisms of biological signal transduction
process by microbial rhodopsins in Bacteria (Anabaena, Jung et al., Mol. Microbiol. 2003) and Eucarya
(Chlamydomonas, Sineshchekov, Jung, & Spudich, PNAS 2002). More specifically, I will focus on the
study of interaction between the photoreceptors with their transducers (a soluble protein in Anabaena and
an ion channel in Chlamydomonas) by genetic, spectroscopic, and biochemical approaches, elucidation
of the functioning of these proteins during the photosignal transduction process, and investigation of the
other component(s) in their signal transduction pathways.
로돕신이란 ?
Microbial rhodopsins, photoactive 7-transmembrane helix proteins that use all-trans retinal as their
chromophore, were observed initially in the Archaea and appeared to be restricted to extreme halophilic
environments.
Genome sequencing of cultivated microbes as well as environmental genomics have unexpectedly
revealed archaeal rhodopsin orthologs in the other two domains of life as well, namely Bacteria and
Eucarya over the past three years.
Organisms containing these homologs inhabit such diverse environments as salt flats, soil, freshwater,
and surface and deep ocean waters, and they comprise a broad phylogenetic range of microbial life,
including haloarchaea, proteobacteria (Magnetospirillum), cyanobacteria (Anabaena), fungi (Neurospora,
Fusarium, & Cryptococcus, and 6 other species), and algae (Chlamydomonas, Guillardia, & Pyrocystis).
Most of these newly found rhodopsin genes have not been expressed and their functions are unknown.
Analysis of the new microbial rhodopsins and their expression and functional characterization will reveal
whether they are ion pumps or sensory functions, which, based on my work with haloarchaea and
Anabaena rhodopsins, may use a variety of signaling mechanisms.
Cyanobacteria and green algae are potentially marvelous experimental systems to study sensing and
photoresponse mechanisms because light is a basic substrate for these photosynthetic microbes. Since
the light input signal can be controlled so easily, rapidly, and precisely, light has a lot of merits for
practical experiments.
The goal of my research is to characterize the molecular basis of the receptor/transducer (soluble and
ion channel) interaction. The development of methods to reconstitute the photo-sensory transduction
components represents an important first step toward a detailed kinetic analysis of protein-protein
interactions underlying the signal transduction process. Also, it could be possible to identify molecular
component(s) that regulate photosignaling pathways in Anabaena and Chlamydomonas.
The proposed research is expected to unveil novel mechanisms of green light responses and it will
advance the knowledge of protein-protein interaction in photosensing and signal relay in prokaryotes and
eukaryotes. The new microbial rhodopsins offer an opportunity for studying the biophysical chemistry of
signal generation and relay, in order to elucidate fundamental principles of sensory transduction and more
broadly the nature of dynamic interactions between receptors and transducers.
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