Factor H is a 20-SCR domain plasma protein that is crucial for the regulation of complement activation in innate immunity by assisting the degradation of C3b. The first five short complement regulator (SCR-1/5) domains are required for decay acceleration and cofactor activity involving C3b, while the SCR-16/20 domains possess C3b/C3d and heparin binding sites. Mutations in SCR-16/20 are associated with kidney failure in atypical haemolytic uraemic syndrome. Sedimentation velocity data identified a monomer-dimer equilibrium in SCR-16/20 using c(s) size-distribution analyses which revealed two peaks as observed. However, SCR-1/5 behaved as a monomer in its c(s) plots, as seen from the single observed peak.
Publication: Okemefuna, A.I., Gilbert, H.E., Griggs, K.M., Ormsby, R.J., Gordeon, D.L. & Perkins, S.J. (2008). The regulatory SCR-1/5 and cell-surface-binding SCR-16/20 fragments of Factor H reveal partially folded-back solution structures and different self-associative properties. J. Mol. Biol. 375, 80-101.