The photosensitive unit triggering the negative phototaxis in the haloarchaeum Natronomonas pharaonis consists of the receptor sensory rhodopsin II (NpSRII) and its cognate transducer (NpHtrII) in a 2:2 stoichiometry. Upon light excitation, a structural rearrangement in the receptor initiates a displacement/rotation of the transducer helix TM2, which can be considered as starting event for the signal transduction. This signal is further transmitted to the cytoplasmic signaling domain through the signal transduction unit comprising two HAMP domains.Structural information already exists for the transmembrane region of this complex (crystal structure) as well as for the rod shaped cytoplasmic part of NpHtrII due to its high homologies with chemoreceptors. Moreover, the solution NMR structure of the isolated HAMP domain from A. fulgidus recently obtained shows a homodimeric, four-helical, parallel coiled-coil with an unusual interhelical packing, that is thought to propagate a signal by virtue of concerted helix rotations. Here, an electron paramagnetic resonance (EPR) investigation of site-directed spin labeled transducers in the NpSRII/NpHtrII complex has been carried out for structural and functional elucidation of the N. pharaonis HAMP. For this purpose, cw as well as pulse EPR techniques have been used in terms of mobility, accessibility and intra-transducer dimer distance analyses. Conformational changes induced by environmental inputs, namely salt, temperature and pH, give insight into the two-state equilibrium existing between a highly dynamic (dHAMP) and a more compact (cHAMP) conformation of this linker region.
| Identifer | oai:union.ndltd.org:uni-osnabrueck.de/oai:repositorium.ub.uni-osnabrueck.de:urn:nbn:de:gbv:700-2009032018 |
| Date | 18 March 2009 |
| Creators | Doebber, Meike Anne |
| Contributors | Prof. Dr. Heinz-Jürgen Steinhoff, Prof. Dr. Sebastian Schlücker |
| Source Sets | Universität Osnabrück |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/zip, application/pdf |
| Rights | http://rightsstatements.org/vocab/InC/1.0/ |
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