Severity: Warning
Message: file_get_contents(https://...@gmail.com&api_key=61f08fa0b96a73de8c900d749fcb997acc09): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 143
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 143
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 209
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 994
Function: getPubMedXML
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3134
Function: GetPubMedArticleOutput_2016
File: /var/www/html/application/controllers/Detail.php
Line: 574
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 488
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Connexin proteins form hexameric assemblies known as hemichannels. When docked to form gap junction (GJ) channels, hemichannels play a critical role in cell-cell communication and cellular homeostasis, but often are functional entities on their own in unapposed cell membranes. Defects in the Connexin26 (Cx26) gene are the major cause of hereditary deafness arising from dysfunctional hemichannels in the cochlea. Structural studies of Cx26 hemichannels properly trafficked and inserted in plasma membranes, including their clustering that forms a plaque-like feature in whole gap junctions, are limited. We used atomic force microscopy (AFM) to study the surface topography of Cx26 hemichannels using two different membrane preparations. Rat Cx26 containing appended carboxy terminal V5 and hexahistidine tags were expressed in baculovirus/Sf9 cell systems. The expressed Cx26 proteins form hemichannels in situ in Sf9 cells that were then purified either as (1) Sf9 membrane fragments containing Cx26 hemichannels or (2) solubilized hemichannels. The latter were subsequently reconstituted in liposomes. AFM images of purified membrane fragments showed clusters of protein macromolecular structures in the membrane that at higher magnification corresponded to Cx26 hemichannels. Hemichannels reconstituted into DOPC bilayers displayed two populations of channel heights likely resulting from differences in orientations of inserted hemichannels. Hemichannels in the protein rich portions of purified membranes also showed a reduced channel height above the bilayer compared to membranes with reconstituted hemichannels perhaps due to reduced AFM probe access to the lipid bilayer. These preparations of purified membranes enriched for connexin hemichannels that have been properly trafficked and inserted in membranes provide a platform for high-resolution AFM imaging of the structure, interconnexon interactions, and cooperativity of properly trafficked and inserted noncrystalline connexin hemichannels.
Download full-text PDF |
Source |
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4255643 | PMC |
http://dx.doi.org/10.1021/bi501265p | DOI Listing |
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