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A Photochromic Histidine Kinase Rhodopsin (HKR1) That Is Bimodally Switched by Ultraviolet and Blue Light
Citation key Luck2012
Author Luck, Meike and Mathes, Tilo and Bruun, Sara and Fudim, Roman and Hagedorn, Rolf and Tra My Tran Nguyen and Kateriya, Suneel and Kennis, John T. M. and Hildebrandt, Peter and Hegemann, Peter
Year 2012
DOI 10.1074/jbc.M112.401604
Journal Journal of Biological Chemistry
Volume 287
Number 47
Abstract Rhodopsins are light-activated chromoproteins that mediate signaling processes via transducer proteins or promote active or passive ion transport as ion pumps or directly light-activated channels. Here, we provide spectroscopic characterization of a rhodopsin from the Chlamydomonas eyespot. It belongs to a recently discovered but so far uncharacterized family of histidine kinase rhodopsins (HKRs). These are modular proteins consisting of rhodopsin, a histidine kinase, a response regulator, and in some cases an effector domain such as an adenylyl or guanylyl cyclase, all encoded in a single protein as a two-component system. The recombinant rhodopsin fragment, Rh, of HKR1 is a UVA receptor (lambda(max) = 380 nm) that is photoconverted by UV light into a stable blue light-absorbing meta state Rh-Bl (lambda(max) = 490 nm). Rh-Bl is converted back to Rh-UV by blue light. Raman spectroscopy revealed that the Rh-UV chromophore is in an unusual 13-cis, 15-anti configuration, which explains why the chromophore is deprotonated. The excited state lifetime of Rh-UV is exceptionally stable, probably caused by a relatively unpolar retinal binding pocket, converting into the photoproduct within about 100 ps, whereas the blue form reacts 100 times faster. We propose that the photochromic HKR1 plays a role in the adaptation of behavioral responses in the presence of UVA light.
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