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Biochemische Mechanismen einer einfachen Verhaltensreaktion
Author(s) -
Marwan Wolfgang,
Oesterhelt Dieter
Publication year - 1999
Publication title -
chemie in unserer zeit
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.217
H-Index - 24
eISSN - 1521-3781
pISSN - 0009-2851
DOI - 10.1002/ciuz.19990330303
Subject(s) - rhodopsin , transmembrane protein , cryptochrome , microbiology and biotechnology , chemistry , cytoplasm , signal transduction , biophysics , biology , retinal , biochemistry , receptor , gene , circadian clock
In active search for conditions for optimal phototrophic growth, halobacteria respond to light and to a variety of other environmental stimuli by taxis. Light reception is mediated by sensory rhodopsins, seven helix transmembrane retinal proteins that are stably complexed to specific MCP‐related transducer proteins. Photoisomerization of the retinal chromophore generates a steric signal which activates the sensory rhodopsin‐transducer‐complex. Complex activation is relayed to a two component signaling system and transiently changes the cytoplasmic concentration of fumarate which, together with the small cytoplasmic protein CheY controls flagellar motor switching. Dual signaling by CheY and fumarate was also found in Escherichia coli where it mediates metabolic signaling and taxis in cells with disabled two‐component system. Sensory integration of different environmental stimuli occurs at the level of the signaling domains of several stimulus‐specific transducers constructed through combination of appropriate molecular modules. Irrespective of the complexity of the signaling network, the response to light is quantitatively predictable and stochastic. Its kinetic analysis suggests that time‐dependent changes in the activity of signaling components can be resolved even in the context of a complex molecular network.