RCSB PDB - 2IC4: Solution structure of the His402 allotype of the Factor H SCR6-SCR7-SCR8 fragment (original) (raw)
Associative and Structural Properties of the Region of Complement Factor H Encompassing the Tyr402His Disease-related Polymorphism and its Interactions with Heparin.
[Fernando, A.N.](/search?q=citation.rcsb%5Fauthors:Fernando, A.N.), [Furtado, P.B.](/search?q=citation.rcsb%5Fauthors:Furtado, P.B.), [Clark, S.J.](/search?q=citation.rcsb%5Fauthors:Clark, S.J.), [Gilbert, H.E.](/search?q=citation.rcsb%5Fauthors:Gilbert, H.E.), [Day, A.J.](/search?q=citation.rcsb%5Fauthors:Day, A.J.), [Sim, R.B.](/search?q=citation.rcsb%5Fauthors:Sim, R.B.), [Perkins, S.J.](/search?q=citation.rcsb%5Fauthors:Perkins, S.J.)
(2007) J Mol Biology 368: 564-581
PubMed: 17362990 Search on PubMed
PubMed Abstract:
Factor H (FH) is a major complement control protein in serum. The seventh short complement regulator (SCR-7) domain of the 20 in FH is associated with age-related macular degeneration through a Tyr402His polymorphism. The recombinant SCR-6/8 domains containing either His402 or Tyr402 and their complexes with a heparin decasaccharide were studied by analytical ultracentrifugation and X-ray scattering. The sedimentation coefficient is concentration dependent, giving a value of 2.0 S at zero concentration and a frictional ratio f/f(o) of 1.2 for both allotypes. The His402 allotype showed a slightly greater self-association than the Tyr402 allotype, and small amounts of dimeric SCR-6/8 were found for both allotypes in 50 mM, 137 mM and 250 mM NaCl buffers. Sedimentation equilibrium data were interpreted in terms of a monomer-dimer equilibrium with a dissociation constant of 40 microM for the His402 form. The Guinier radius of gyration R(G) of 3.1-3.3 nm and the R(G)/R(O) ratio of 2.0-2.1 showed that SCR-6/8 is relatively extended in solution. The distance distribution function P(r) showed a maximum dimension of 10 nm, which is less than the length expected for a linear domain arrangement. The constrained scattering and sedimentation modelling of FH SCR-6/8 showed that bent SCR arrangements fit the data better than linear arrangements. Previously identified heparin-binding residues were exposed on the outside curvature of this bent domain structure. Heparin caused the formation of a more linear structure, possibly by binding to residues in the linker. It was concluded that the His402 allotype may self-associate more readily than the Tyr402 allotype, SCR-6/8 is partly responsible for the folded-back structure of intact FH, and SCR-6/8 changes conformation upon heparin binding.
Organizational Affiliation:
Department of Biochemistry and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, UK.