Linked Life Data

1569104

Source:http://linkedlifedata.com/resource/pubmed/id/1569104

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
12
pubmed:dateCreated
1992-5-28
pubmed:abstractText
Three human plasma proteins contain intramolecular thioester bonds: complement components C3 and C4 and alpha 2-macroglobulin. Their thioesters form when glutamine and cysteine residues react in the newly translated proteins and ammonia is released. We have reversed this reaction by treating C3 with ammonia to cleave the thioester and reform the original Gln and Cys. Thioester scission initiates a multistep conformational transition. One intermediate was sufficiently stable to be isolated by high performance liquid chromatography. It lacked native C3 functions and was shown to contain one free sulfhydryl group. Incubation of this ammonia-inactivated C3 intermediate in the absence of ammonia resulted in refolding to a native C3 conformation and recovery of thioester-dependent functions, as evidenced by: 1) return of hemolytic function, 2) return of autolytic cleavage of the alpha-chain, and 3) return of the ability to attach to surfaces during complement activation. Refolding and thioester reformation were dependent on a free SH group and were inhibited by HgCl2 and other thiol-specific reagents. Incubation of ammonia-inactivated C3 at 25 degrees C at pH 7.4 resulted in recovery of 70% of the original C3 function. Refolding and thioester reformation exhibited a Gibbs free energy of +5.2 kcal/mol and were favored over unfolding to the final inactive form. During reformation of native C3 from 14CH3NH2-treated C3, return of the native conformation was accompanied by release of radiolabel from the protein and return of hemolytic complement function. These results suggest that folding of C3 provides both the energy and environment necessary to react the Gln and Cys residues, release ammonia, and form the thioester bond.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
25
pubmed:volume
267
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8584-90
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Spontaneous reformation of the intramolecular thioester in complement protein C3 and low temperature capture of a conformational intermediate capable of reformation.
pubmed:affiliation
Department of Biochemistry, University of Texas Health Science Center, Tyler 75710.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.