Linked Life Data

8662615

Source:http://linkedlifedata.com/resource/pubmed/id/8662615

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
20
pubmed:dateCreated
1996-8-29
pubmed:abstractText
Transcobalamin II receptor (TC II-R) exists as a monomer and a dimer of molecular masses of 62 and 124 kDa in the microsomal and plasma membranes, respectively, and in vitro, pure TC II-R monomer dimerizes upon insertion into egg PC/cholesterol (molar ratio, 4:1) liposomes (Bose, S., Seetharam, S., and Seetharam, B. (1995) J. Biol Chem. 270, 8152-8157 and Bose, S., Seetharam, S., Hammond, T., and Seetharam, B. (1995) Biochem. J. 310, 923-929). The current studies were carried out to define the mechanism of TC II-R dimerization. Both the mature TC II-R (62 kDa) and the enzymatically deglycosylated TC II-R (45-47 kDa) demonstrated optimal association and formed dimers of molecular masses of 95 and 124 kDa, respectively, at 22 degrees C when bound to egg PC vesicles containing at least 10 mol % of cholesterol. Mature TC II-R dimerized upon insertion into synthetic phosphatidylcholine vesicles of different fatty acyl chain length (dimyristoyl, dipalmitoyl, and disteroyl phosphatidylcholine) in the absence or the presence of cholesterol at temperatures below or above their transition temperatures, respectively. Dimerization of TC II-R also occurred with vesicles prepared using lipid extract from the plasma but not microsomal membranes. Cholesterol depletion of native intestinal plasma membranes or its enrichment in the microsomal membranes resulted in the in situ conversion of the 124-kDa dimer to the 62-kDa monomer or of the monomer into the dimer form, respectively. Treatment of plasma membranes with phospholipase A2 resulted in the conversion of the dimer form of the receptor to the monomer form and spin label studies using 1-palmitoyl, 12 doxylsteroyl phosphatidylcholine revealed that interactions of TC II-R with PC vesicles increased order around the probe. Based on these results we suggest that dimerization of TC II-R is mediated by its interactions with a rigid more ordered lipid bilayer membrane, is regulated in plasma membranes by cholesterol levels, and is independent of glycosylation-mediated folding.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
17
pubmed:volume
271
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
11718-25
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1996
pubmed:articleTitle
Dimerization of transcobalamin II receptor. Requirement of a structurally ordered lipid bilayer.
pubmed:affiliation
Department of Biochemistry, Medical College of Wisconsin and Veterans Administration Medical Center, Milwaukee 53226, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.