POSTERS - BLAST X - University of Utah

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