POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
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<strong>BLAST</strong> X Thurs. Evening Session<br />
PHOTO-ENERGY CONVERSION AND SENSORY TRANSDUCTION OF MICROBIAL<br />
RHODOPSINS IN PHOTOSYNTHETIC MICROBES<br />
So Young Kim, Keon Ah Lee, Ah Reum Choi, Song-I Han, and Kwang-Hwan Jung<br />
Department <strong>of</strong> Life Science and Interdisciplinary Program <strong>of</strong> Integrated Biotechnology, Sogang<br />
Univeristy, Seoul 121-742, Korea (kjung@sogang.ac.kr)<br />
Microbial rhodopsins, seven transmembrane proteins which contain all-trans/13 cis<br />
retinal as a chromophore, have been known for three decades and extensively studies in<br />
extreme halophiles. Photosynthetic microbes possess lots <strong>of</strong> photoactive proteins including<br />
chlorophyll-based pigments, phytochromes, phototropin-related blue light receptors, and<br />
cryptochromes. Surprisingly, recent genome sequencing projects discovered additional<br />
photoactive receptors, retinal-based rhodopsins, in cyanobacterial and algal genera. Analysis <strong>of</strong><br />
the Anabaena and Chlamyrhodopsin revealed that they have sensory functions, which based on<br />
our work with haloarchaeal rhodopsins, may use a variety <strong>of</strong> signaling mechanisms. Anabaena<br />
rhodopsin is interacted with a tetramer <strong>of</strong> 14kDa soluble transducer (ASRT) and one <strong>of</strong> their<br />
putative functions is a global regulation <strong>of</strong> phycobilin protein. The Anabaena rhodopsin shows a<br />
visible light-absorbing pigment (540-550nm) and it has mixed photochemical reaction <strong>of</strong> all trans<br />
and 13 cis form <strong>of</strong> retinal in ground state. Two Chlamydomonas rhodopsins are involved in<br />
phototaxis and photophobic responses based on electrical measurements by RNAi experiment.<br />
The rhodopsins from Gloeobacter violaceus and Acetabularia acetabulum is light-driven proton<br />
pump coexisted with photosynthetic machinery. The genes were functionally expressed in<br />
Escherichia coli and bound all-trans retinal to form a pigment in the presence <strong>of</strong> N- and Cterminal<br />
MISTIC sequences. Gloeobacter and Acetabularia rhodopsin I showed a light-driven<br />
proton pumping activity similar to proteorhodopsin.<br />
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