Linked Life Data

3282009

Source:http://linkedlifedata.com/resource/pubmed/id/3282009

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
8
pubmed:dateCreated
1988-5-18
pubmed:abstractText
The 25,000-Da protein that is seen in immunoprecipitates with antibodies to class II MHC molecules or to Ii was shown to be a C-terminal fragment of Ii. [35S]Methionine pulse-chase labeling of polyclonally activated B lymphocytes or lymphoblastoid cell lines demonstrated maximal appearance of p25 in Percoll-separated endosomal fractions at 20- to 40-min chase times (studies in progress). This finding was consistent with the view that proteolysis of Ii to p25 and its release might catalyze the binding of digested foreign peptides to class II molecules and/or govern release of such charged complexes to traffic to the cell surface. We examined the structural relationship of p25 to Ii and the basis for cleavage of a relatively restricted site just external to the transmembranal segment. [35S]Methionine-labeled Ii and associated molecules were immunoprecipitated with a mAb to native Ii and then denatured, resolubilized, and subjected to a second immunoprecipitation with various antibodies. Two antisera to C-terminal peptides of Ii (183 to 193 and 192 to 211), but not antibodies to an N-terminal peptide (12 to 28), did immunoprecipitate p25. The three antibodies to C-terminal and N-terminal peptides all immunoprecipitated denatured Ii proteins. The mAb to Ii immunoprecipitated [35S]methionine-labeled p25 but not [35S]cysteine-labeled p25. This finding was consistent with loss of a portion of Ii containing the only cysteine in Ii, Cys28. Digestion of class II MHC Ag-Ii complexes with various proteases yielded proteins migrating at and near p25 in two-dimensional electrophoretic gels. Upon increasing the duration of protease digestion, the 25,000-Da fragments were relatively resistant to further digestion. This observation was consistent with the presence of secondary structures (domains) leaving a relatively protease-sensitive (Ig hinge-like) region in Ii near its insertion into the membrane.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
AIM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0022-1767
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
140
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2670-4
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1988
pubmed:articleTitle
Proteolytic cleavage of Ii to p25.
pubmed:affiliation
Department of Pharmacology, University of Massachusetts Medical School, Worcester 01655.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.