Document Detail


Sensory rhodopsin-controlled release of the switch factor fumarate in Halobacterium salinarium.
MedLine Citation:
PMID:  7934858     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Halobacterium salinarium responds to blue light by reversing its swimming direction. Fumarate has been proposed as one of the molecular components of this sensory system and is involved in the switching process of the flagellar motor. In order to obtain chemical proof for this role of fumarate, cells were stimulated with a pulse of blue light and lysed by rapid mixing with distilled water. The lysate contained fumarate in free and bound form, which were separated by ultrafiltration. The fumarate concentration in the low-molecular-mass fraction (< 5 kDa) of the lysate was assayed enzymatically and a light-induced increase was observed. Additionally, the total cellular fumarate content decreased in response to light, indicating that fumarate was released from a cellular pool rather than being formed by de novo synthesis. The light-induced release was not detected in a mutant defective in sensory rhodopsin-I and -II. Therefore it is concluded that photoreceptor activation rather than a direct effect of light on the activity of metabolic enzymes causes fumarate release. For each photoactivated sensory rhodopsin-II molecule at least 350 molecules of fumarate were liberated demonstrating efficient amplification. The rate of light-induced fumarate release is at least 10-times faster than the fumarate turnover number of the citric acid cycle which was estimated as approximately 4300 per cell and second. Therefore this metabolic process is not expected to be part of the signal transduction chain in the halobacterial cell.
Authors:
M Montrone; W Marwan; H Grünberg; S Musseleck; C Starostzik; D Oesterhelt
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Molecular microbiology     Volume:  10     ISSN:  0950-382X     ISO Abbreviation:  Mol. Microbiol.     Publication Date:  1993 Dec 
Date Detail:
Created Date:  1994-11-23     Completed Date:  1994-11-23     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8712028     Medline TA:  Mol Microbiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  1077-85     Citation Subset:  IM    
Affiliation:
Max-Planck-Institut für Biochemie, Martinsried, Germany.
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MeSH Terms
Descriptor/Qualifier:
Cell Membrane / metabolism
Cell Movement / genetics,  physiology,  radiation effects
Citric Acid Cycle
Cytoplasm / metabolism
Flagella / metabolism,  radiation effects
Fumarate Hydratase / metabolism
Fumarates / metabolism*
Halobacterium / genetics,  metabolism*,  radiation effects*
Kinetics
Light
Mutation
Rhodopsin / genetics,  metabolism*
Signal Transduction
Chemical
Reg. No./Substance:
0/Fumarates; 110-17-8/fumaric acid; 9009-81-8/Rhodopsin; EC 4.2.1.2/Fumarate Hydratase

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