Linked Life Data

3512717

Source:http://linkedlifedata.com/resource/pubmed/id/3512717

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
7
pubmed:dateCreated
1986-4-15
pubmed:abstractText
In a previous study we demonstrated that the thioester-mediated transacylation of the human C4B isotype onto sheep erythrocytes (ES) was approximately fourfold more efficient than that of C4A. Moreover, although C4B formed predominantly ester linkages, C4A displayed a preference for amide bond formation. We therefore suggested that the relative functional activity observed for the two isotypes would be a combined reflection of their nucleophilic preference and the surface composition of the C1-bearing target. The present study tests this hypothesis. Chemical modification of amino groups on Es with ethylacetimidate produced a twofold decrease in the C1-dependent binding of C4A isotype, while having a negligible effect on C4B binding. Furthermore, with human erythrocytes and two human leukocyte cell lines, K562 and U937, the C4B to C4A deposition ratio decreased from greater than 4 with ES to between 1.5 and 2. Irrespective of the target, C4A and C4B maintained their preference for forming amide and ester bonds, respectively. Interestingly, SDS-PAGE profiles of radiolabeled C4A and C4B, which had been covalently deposited on the various cells, suggested a further degree of transacylation specificity, as the two isotypic alpha-chains sometimes bound to different membrane components. These differences were not easily accounted for by simple differences in the abundance of the preferred nucleophile for each isotype on a given surface constituent, nor were they due to the preferential binding of one isotype to the sensitizing antibody. We speculate that nascent C4B may contain a substrate binding site that facilitates productive attack on the thioester carbonyl by molecules containing the class of nucleophile preferred by each isotype.
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
1
pubmed:volume
136
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2542-50
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1986
pubmed:articleTitle
Covalent binding properties of the C4A and C4B isotypes of the fourth component of human complement on several C1-bearing cell surfaces.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't