Linked Life Data

12444082

Source:http://linkedlifedata.com/resource/pubmed/id/12444082

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6
pubmed:dateCreated
2003-2-3
pubmed:abstractText
Coagulation factor IXa (fIXa) plays a central role in the coagulation cascade. Enzymatically, fIXa is characterized by its very low amidolytic activity that is not improved in the presence of cofactor, factor VIIIa (fVIIIa), distinguishing fIXa from all other coagulation factors. Activation of the fIXa-fVIIIa complex requires its macromolecular substrate, factor X (fX). The 99-loop positioned near the active site partly accounts for the poor activity of fIXa because it adopts a conformation that interferes with canonical substrate binding in S2-S4. Here we show that residues Lys-98 and Tyr-99 are critically linked to the amidolytic properties of fIXa. Exchange of Tyr-99 with smaller residues resulted not only in an overall decreased activity but also in impaired binding in S1. Replacement of Lys-98 with smaller and uncharged residues increased activity. Simultaneous mutagenesis of Lys-98, Tyr-177, and Tyr-94 produced an enzyme with 7000-fold increased activity and altered specificity. This triple mutant probably mimics the conformational changes that are physiologically induced by cofactor and substrate binding. It therefore provides a cooperative two-step activation model for fIXa. Tyr-177 locks the 99-loop in an inactive conformation which, in the physiologic complex, is released by cofactor fVIIIa. FX is then able to rearrange the unlocked 99-loop and subsequently binds to the active site cleft.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
7
pubmed:volume
278
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4121-6
pubmed:meshHeading
pubmed:year
2003
pubmed:articleTitle
Physiological fIXa activation involves a cooperative conformational rearrangement of the 99-loop.
pubmed:affiliation
Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany. Katrin.Sichler@roche.com
pubmed:publicationType
Journal Article