Linked Life Data

17311415

Source:http://linkedlifedata.com/resource/pubmed/id/17311415

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
11
pubmed:dateCreated
2007-3-13
pubmed:abstractText
Phototropins are autophosphorylating serine/threonine kinases responsible for blue-light perception in plants; their action gives rise to phototropism, chloroplast relocation, and opening of stomatal guard cells. The kinase domain constitutes the C-terminal part of Avena sativa phototropin 1. The N-terminal part contains two light, oxygen, or voltage (LOV) sensing domains, LOV1 and LOV2; each binds a flavin mononucleotide (FMN) chromophore (lambdamax = 447 nm, termed D447) and forms the light-sensitive domains, of which LOV2 is the principal component. Blue-light absorption produces a covalent adduct between a very conserved nearby cysteine residue and the C(4a) atom of the FMN moiety via the triplet state of the flavin. The covalent adduct thermally decays to regenerate the D447 dark state, with a rate that may vary by several orders of magnitude between different species. We report that the imidazole base can act as a very efficient enhancer of the dark recovery of A. sativa phot1 LOV2 (AsLOV2) and some other well-characterized LOV domains. Imidazole accelerates the thermal decay of AsLOV2 by 3 orders of magnitude in the submolar concentration range, via a base-catalyzed mechanism involving base abstraction of the FMN N(5)-H adduct state and subsequent reprotonation of the reactive cysteine. The LOV2 crystal structure suggests that the imidazole molecules may act from a cavity located in the vicinity of the FMN, explaining its high efficiency, populated through a channel connecting the cavity to the protein surface. Use of pH titration and chemical inactivation by diethyl pyrocarbonate (DEPC) suggests that histidines located at the surface of the LOV domain act as base catalysts via an as yet unidentified H-bond network, operating at a rate of (55 s)-1 at pH 8. In addition, molecular processes other than histidine-mediated base catalysis contibute significantly to the total thermal decay rate of the adduct and operate at a rate constant of (65 s)-1, leading to a net adduct decay time constant of 30 s at pH 8.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
20
pubmed:volume
46
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
3129-37
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
2007
pubmed:articleTitle
A base-catalyzed mechanism for dark state recovery in the Avena sativa phototropin-1 LOV2 domain.
pubmed:affiliation
Department of Biophysics, Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081HV Amsterdam, The Netherlands. miaalex@nat.vu.nl
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural