Linked Life Data

10529200

Source:http://linkedlifedata.com/resource/pubmed/id/10529200

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
40
pubmed:dateCreated
1999-11-10
pubmed:abstractText
Sensory rhodopsin I (SRI) is a seven-transmembrane helix retinylidene protein that mediates color-sensitive phototaxis responses through its bound transducer HtrI in the archaeon Halobacterium salinarum. Deprotonation of the Schiff base attachment site of the chromophore accompanies formation of the SRI signaling state, S(373). We measured the rate of laser flash-induced S(373) formation in the presence and absence of HtrI, and the effects of mutations in SRI or HtrI on the kinetics of this process. In the absence of HtrI, deprotonation occurs rapidly (halftime 10 micros) if the proton acceptor Asp76 is ionized (pK(a) = approximately 7), and only very slowly (halftime > 10 ms) when Asp76 is protonated. Transducer-binding, although it increases the pK(a) of Asp76 so that it is protonated throughout the range of pH studied, results in a first order, pH-independent rate of S(373) formation of approximately 300 micros. Therefore, the complexation of HtrI facilitates the proton-transfer reaction, increasing the rate approximately 50-fold at pH6. Arrhenius analysis shows that HtrI-binding accelerates the reaction primarily by an entropic effect, suggesting HtrI constrains the SRI molecule in the complex. Function-perturbing mutations in SRI and HtrI also alter the rate of S(373) formation and the lambda(max) of the parent state as assessed by laser flash-induced kinetic difference spectroscopy, and shifts to longer wavelength are correlated with slower deprotonation. The data indicate that HtrI affects electrostatic interactions of the protonated Schiff base and not only receives the signal from SRI but also optimizes the photochemical reaction process for SRI signaling.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
38
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
13270-4
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
Transducer-binding and transducer-mutations modulate photoactive-site-deprotonation in sensory rhodopsin I.
pubmed:affiliation
Department of Microbiology and Molecular Genetics, The University of Texas-Houston Medical School 77030, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.