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@PHDTHESIS{Fastermann:35976,
author = {Fastermann, Dirk},
title = {{H}alorhodopsin : {K}lonierung, {E}xpression,
{K}ristallisation und spektroskopische {U}ntersuchungen zum
{M}echanismus dieser {A}nionenpumpe},
volume = {3934},
issn = {0944-2952},
school = {Univ. Düsseldorf},
type = {Dr. (Univ.)},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {PreJuSER-35976, Juel-3934},
series = {Berichte des Forschungszentrums Jülich},
pages = {III, 111 p.},
year = {2002},
note = {Record converted from VDB: 12.11.2012; Düsseldorf, Univ.,
Diss. 2002},
abstract = {Four retinal proteins have been discovered in Halobacterium
salinarum : The sensory rhodopsins I and II which function
as photoreceptors and bacteriorhodopsin (bR) and
halorhodopsin (hR) which function as ion pumps. In this
work, functional investigations of thé anion pump hR were
undertaken, with thé main focus on thé mechanistic
analysis of thé light driven anion transport . In order to
overexpress hR, thé hR gene was first linked to thé
promotor of bR. The expression took place in thé bR
negative strain L33 from H. salinarum . The expression level
of this fusion construct was so high that hR crystallized in
vivo in a two-dimensional lattice. Due to this, it was
possible to isolate and to purify hR in a membrane-bound
state. For thé crystallization and spectroscopic
measurements a purification method was established which
preserves native structural and functional integrity.
Crystallization trials with solubilized hR using sitting
drop and cubic lipidic phase method were performed. With
thé cubic lipidic phase, it was possible to get three
dimensional crystals, but they showed no diffraction. The
chloride dependency of thé hR photocycle was studied with
spectroscopic measurements employing a non-time resolved
chloride titration of hR membrane patches . The différence
absorbance spectra showed three différent states (at 540
nm, 580 nm and 650 mn) which depend on thé chloride
concentration . The chloride progression of thé states
showed three potential binding constants for chloride to hR.
Two photocycle models, one in thé absence and one in thé
présence of chloride, were formulated from thé time
resolved visible measurements. Specifically, thé photocycle
model without chloride suggests two states: hR54o and
hR-y.650, whereas thé photocycle model with chloride
suggests three states: hR5Bo, hR-K65o and hRL52o. The
photocycle without chloride is much faster. Chloride
dependent investigations were also done with time-resolved
FTIR spectroscopy in combination with thé ATR technique.
With increasing chloride concentration, thé formation of
thé hRLintermediate was accelerated. On thé other hand,
thé decay of thé L intermediate is showed down with
increasing chloride concentration . At very high chloride
concentrations, e.g. 5 M, différences in thé amide I
region between early and late hR-L différence spectra were
detected. This implies structural changes in thé protein
backbone. This was corroborated with linear dichroism. The
chloride dependent formation of thé hR-Ll and thé decay of
thé hR-L2 intermediate implies that thé chloride uptake
takes place during thé transition from thé hR-K
intermediate to thé hR-Ll intermediate . In addition thé
transfer of thé chloride to thé cytoplasm occurs between
thé hRL2 intermediate and thé ground state.},
cin = {IBI-2},
cid = {I:(DE-Juel1)VDB58},
pnm = {Biologische Strukturforschung},
pid = {G:(DE-Juel1)FUEK96},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
url = {https://juser.fz-juelich.de/record/35976},
}