Linked Life Data

19938870

Source:http://linkedlifedata.com/resource/pubmed/id/19938870

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
51
pubmed:dateCreated
2009-12-22
pubmed:abstractText
Halorhodopsin from Natronomonas pharaonis (NpHR) acts an inward-directed, light-driven chloride pump and forms a homotrimer. To evaluate effect of trimeric assembly, that is, intermolecular interaction, on the control or modulation of light-driven chloride pumping activity of individual HRs, it is important to understand the thermal and chloride sensitivity of trimer dissociation and the structural stability of HR. In this study, the thermal dissociation of NpHR trimer to monomer in a dodecyl beta-d-maltoside-solubilized system was investigated, using size-exclusion chromatography and visible absorption. In the absence of Cl(-), NpHR retained the trimer assembly at 25 degrees C but dissociated to the monomer with an increase in temperature to >40 degrees C. On the other hand, in the presence of Cl(-), the trimer assembly was maintained at 40 degrees C. The dissociation of the trimer to the monomer after incubation at 40 degrees C, which was determined via size-exclusion chromatography, depended on the Cl(-) concentration and showed a sigmoidal isotherm. From this isotherm, the apparent dissociation constant for Cl(-) was estimated to be 22 mM with a Hill coefficient of 2.2. A similar isotherm was obtained when SO(4)(2-) was used instead of Cl(-) with a dissociation constant of 94 mM. On the other hand, thermal dissociation of the NpHR trimer to the monomer in the absence of Cl(-) proceeded by two components: the fast component is susceptible to the changes in temperature and detergent concentration, and the slow component is accompanied by bleaching at the same time. Activation energies of the fast and slow dissociation components and bleaching were 57.8, 35.3, and 40.5 kcal/mol, respectively. The presence of a second chloride-binding site with a Hill coefficient of approximately 2 at the surface of NpHR to control the trimer-monomer conversion was discussed.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
1520-4995
pubmed:author
pubmed:issnType
Electronic
pubmed:day
29
pubmed:volume
48
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
12089-95
pubmed:meshHeading
pubmed:year
2009
pubmed:articleTitle
Effect of chloride binding on the thermal trimer-monomer conversion of halorhodopsin in the solubilized system.
pubmed:affiliation
Faculty of Life Science, Hokkaido University, Sapporo 060-0810, Japan.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't