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Solution structure of a functionally active fragment of decay-accelerating factor.

Stanislava Uhrinova·Feng Lin·Graeme Ball·Krystyna Bromek·Dusan Uhrin·M Edward Medof·Paul N Barlow
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Abstract

The second and third modules of human decay accelerating factor (DAF) are necessary and sufficient to accelerate decay of the classical pathway (CP) convertase of complement. No structure of a mammalian protein with decay-accelerating activity has been available to date. We therefore determined the solution structure of DAF modules 2 and 3 (DAF approximately 2,3). Structure-guided analysis of 24 mutants identified likely contact points between DAF and the CP convertase. Three (R96, R69, and a residue in the vicinity of L171) lie on DAF approximately 2,3's concave face. A fourth, consisting of K127 and nearby R100, is on the opposite face. Regions of module 3 remote from the semiflexible 2-3 interface seem not to be involved in binding to the CP convertase. DAF thus seems to occupy a groove on the CP convertase such that both faces of DAF close to the 2-3 junction (including a positively charged region that encircles the protein at this point) interact simultaneously. Alternative pathway convertase interactions with DAF require additional regions of CCP 3 lying away from the 2-3 interface, consistent with the established additional requirement of module 4 for alternative pathway regulation.

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Binding SitesCD55 AntigensComplement C3-C5 ConvertasesHumansModels, MolecularMutagenesis, Site-DirectedNuclear Magnetic Resonance, BiomolecularPeptide FragmentsProtein ConformationRecombinant ProteinsSolutionsStatic ElectricityThermodynamicsJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.

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Stanislava Uhrinova, Feng Lin, Graeme Ball, Krystyna Bromek, Dusan Uhrin, M Edward Medof, Paul N Barlow. 2003-04-02. Solution structure of a functionally active fragment of decay-accelerating factor.. https://doi.org/10.1073/pnas.0730844100

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