서강대학교

초록/요약

Microbial rhodopsins are that seven trans membrane protein which has retianl as chromophore can convert light to energe by forming schiff base with binding retinal and lysine conserved site in 7th helix through photoisomerization by light. Microbial rhodopsins are divided two category based on function. First, there are ion pump rhodopsins like BR, PR, NTQ, CHR. Second, sensory rhodopsins like ASR, SR I, SR II have functions signal transduction. Anabaena Sensory Rhodopsin(ASR) is an archaeal-type rhodopsin found in cyanobacteria PCC7120 in 2003. ASR has slow photocycle than general ion pump rhodopsins and regulate phycobilisome generation by binding with 14 kDa transducer(ASRT). In previous study, ASR wild type and some mutants was measured by computer simulation using two basic models(Model I and Model II). Model I and II is based on ASR wild type and mutants depending on whether hydrogen bond interaction. In this study, i mutated cavity residues Y73, W76, L83, V112, P206 and non-cavity residues E36, S86, S214, D217. I measured absorption maxima at neutral, acidic and alkaline ph and campared to computed simulation data. Also, during the photocycle, i measured conformationl change, proportion, wavelength of various photointermediate of ASR mutants and caculated ratio of retinal isomers of ASR mutants. In result, there is no difference at different ph condition except for a little mutants. However, most of the change involved color-tuning occured in cavity residue mutant compared with wild type. In time-resolved difference spectra, cavity residue mutants have tendency which have difference from wild type. Especially, P206 residue which has roles of counterion of D75 hydrogen bonding retinal around schiff base shows unusal properties, thie result was supported by HPLC analysis.