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The central portion of factor H (modules 10-15) is compact and contains a structurally deviant CCP module.

Schmidt CQ, Herbert AP, Mertens HD, Guariento M, Soares DC, Uhrin D, Rowe AJ, Svergun DI, Barlow PN - J. Mol. Biol. (2009)

Bottom Line: In conclusion, fH10-15 forms neither a flexible tether nor a smooth bend.Rather, it is compact and has embedded within it a CCP module (CCP 13) that appears to be highly specialised given both its deviant structure and its striking surface charge distribution.A passive, purely structural role for this central portion of fH is unlikely.

View Article: PubMed Central - PubMed

Affiliation: Edinburgh Biomolecular NMR Unit, Centre for Chemical and Translational Biology, Schools of Biological Sciences and Chemistry, University of Edinburgh, Edinburgh EH9 3JJ, UK.

ABSTRACT
The first eight and the last two of 20 complement control protein (CCP) modules within complement factor H (fH) encompass binding sites for C3b and polyanionic carbohydrates. These binding sites cooperate self-surface selectively to prevent C3b amplification, thus minimising complement-mediated damage to host. Intervening fH CCPs, apparently devoid of such recognition sites, are proposed to play a structural role. One suggestion is that the generally small CCPs 10-15, connected by longer-than-average linkers, act as a flexible tether between the two functional ends of fH; another is that the long linkers induce a 180 degrees bend in the middle of fH. To test these hypotheses, we determined the NMR-derived structure of fH12-13 consisting of module 12, shown here to have an archetypal CCP structure, and module 13, which is uniquely short and features a laterally protruding helix-like insertion that contributes to a prominent electropositive patch. The unusually long fH12-13 linker is not flexible. It packs between the two CCPs that are not folded back on each other but form a shallow vee shape; analytical ultracentrifugation and X-ray scattering supported this finding. These two techniques additionally indicate that flanking modules (within fH11-14 and fH10-15) are at least as rigid and tilted relative to neighbours as are CCPs 12 and 13 with respect to one another. Tilts between successive modules are not unidirectional; their principal axes trace a zigzag path. In one of two arrangements for CCPs 10-15 that fit well with scattering data, CCP 14 is folded back onto CCP 13. In conclusion, fH10-15 forms neither a flexible tether nor a smooth bend. Rather, it is compact and has embedded within it a CCP module (CCP 13) that appears to be highly specialised given both its deviant structure and its striking surface charge distribution. A passive, purely structural role for this central portion of fH is unlikely.

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Overview of SAXS data and analysis. (a) Scattering curves for fH12–13 (red), fH11–14 (blue), and fH10–15 (yellow). Continuous lines represent fits obtained by CRYSOL for the best fH12–13 NMR model, or by rigid-body modelling (BUNCH) for fH11–14 and fH10–15; curves have been arbitrarily displaced along the logarithmic axis for clarity. (b) p(r) functions (arbitrary units) for fH12–13 (red), fH11–14 (blue), and fH10–15 (yellow), computed from X-ray scattering patterns using GNOM. (c) Radius-of-gyration distributions of pools (red lines) and selected structures (black) for fH12–13, fH11–14, and fH10–15 using EOM. Integral of area defined by histograms = 1.
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fig7: Overview of SAXS data and analysis. (a) Scattering curves for fH12–13 (red), fH11–14 (blue), and fH10–15 (yellow). Continuous lines represent fits obtained by CRYSOL for the best fH12–13 NMR model, or by rigid-body modelling (BUNCH) for fH11–14 and fH10–15; curves have been arbitrarily displaced along the logarithmic axis for clarity. (b) p(r) functions (arbitrary units) for fH12–13 (red), fH11–14 (blue), and fH10–15 (yellow), computed from X-ray scattering patterns using GNOM. (c) Radius-of-gyration distributions of pools (red lines) and selected structures (black) for fH12–13, fH11–14, and fH10–15 using EOM. Integral of area defined by histograms = 1.

Mentions: The software CRYSOL was employed to fit each conformer from the NMR-derived ensemble of fH12–13 to SAXS data collected on fH12–13 (in 50 mM potassium phosphate, pH 7.4). Good fits (see Fig. 7a) of the scattering data to each ensemble member were observed (1.24 < χ < 1.43), supporting the structure determined by NMR (in 20 mM potassium phosphate, pH 6.6).


The central portion of factor H (modules 10-15) is compact and contains a structurally deviant CCP module.

Schmidt CQ, Herbert AP, Mertens HD, Guariento M, Soares DC, Uhrin D, Rowe AJ, Svergun DI, Barlow PN - J. Mol. Biol. (2009)

Overview of SAXS data and analysis. (a) Scattering curves for fH12–13 (red), fH11–14 (blue), and fH10–15 (yellow). Continuous lines represent fits obtained by CRYSOL for the best fH12–13 NMR model, or by rigid-body modelling (BUNCH) for fH11–14 and fH10–15; curves have been arbitrarily displaced along the logarithmic axis for clarity. (b) p(r) functions (arbitrary units) for fH12–13 (red), fH11–14 (blue), and fH10–15 (yellow), computed from X-ray scattering patterns using GNOM. (c) Radius-of-gyration distributions of pools (red lines) and selected structures (black) for fH12–13, fH11–14, and fH10–15 using EOM. Integral of area defined by histograms = 1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2806952&req=5

fig7: Overview of SAXS data and analysis. (a) Scattering curves for fH12–13 (red), fH11–14 (blue), and fH10–15 (yellow). Continuous lines represent fits obtained by CRYSOL for the best fH12–13 NMR model, or by rigid-body modelling (BUNCH) for fH11–14 and fH10–15; curves have been arbitrarily displaced along the logarithmic axis for clarity. (b) p(r) functions (arbitrary units) for fH12–13 (red), fH11–14 (blue), and fH10–15 (yellow), computed from X-ray scattering patterns using GNOM. (c) Radius-of-gyration distributions of pools (red lines) and selected structures (black) for fH12–13, fH11–14, and fH10–15 using EOM. Integral of area defined by histograms = 1.
Mentions: The software CRYSOL was employed to fit each conformer from the NMR-derived ensemble of fH12–13 to SAXS data collected on fH12–13 (in 50 mM potassium phosphate, pH 7.4). Good fits (see Fig. 7a) of the scattering data to each ensemble member were observed (1.24 < χ < 1.43), supporting the structure determined by NMR (in 20 mM potassium phosphate, pH 6.6).

Bottom Line: In conclusion, fH10-15 forms neither a flexible tether nor a smooth bend.Rather, it is compact and has embedded within it a CCP module (CCP 13) that appears to be highly specialised given both its deviant structure and its striking surface charge distribution.A passive, purely structural role for this central portion of fH is unlikely.

View Article: PubMed Central - PubMed

Affiliation: Edinburgh Biomolecular NMR Unit, Centre for Chemical and Translational Biology, Schools of Biological Sciences and Chemistry, University of Edinburgh, Edinburgh EH9 3JJ, UK.

ABSTRACT
The first eight and the last two of 20 complement control protein (CCP) modules within complement factor H (fH) encompass binding sites for C3b and polyanionic carbohydrates. These binding sites cooperate self-surface selectively to prevent C3b amplification, thus minimising complement-mediated damage to host. Intervening fH CCPs, apparently devoid of such recognition sites, are proposed to play a structural role. One suggestion is that the generally small CCPs 10-15, connected by longer-than-average linkers, act as a flexible tether between the two functional ends of fH; another is that the long linkers induce a 180 degrees bend in the middle of fH. To test these hypotheses, we determined the NMR-derived structure of fH12-13 consisting of module 12, shown here to have an archetypal CCP structure, and module 13, which is uniquely short and features a laterally protruding helix-like insertion that contributes to a prominent electropositive patch. The unusually long fH12-13 linker is not flexible. It packs between the two CCPs that are not folded back on each other but form a shallow vee shape; analytical ultracentrifugation and X-ray scattering supported this finding. These two techniques additionally indicate that flanking modules (within fH11-14 and fH10-15) are at least as rigid and tilted relative to neighbours as are CCPs 12 and 13 with respect to one another. Tilts between successive modules are not unidirectional; their principal axes trace a zigzag path. In one of two arrangements for CCPs 10-15 that fit well with scattering data, CCP 14 is folded back onto CCP 13. In conclusion, fH10-15 forms neither a flexible tether nor a smooth bend. Rather, it is compact and has embedded within it a CCP module (CCP 13) that appears to be highly specialised given both its deviant structure and its striking surface charge distribution. A passive, purely structural role for this central portion of fH is unlikely.

Show MeSH
Related in: MedlinePlus