A cluster of positively charged amino acids in the C4BP alpha-chain is crucial for C4b binding and factor I cofactor function.

@article{Blom1999ACO,
  title={A cluster of positively charged amino acids in the C4BP alpha-chain is crucial for C4b binding and factor I cofactor function.},
  author={Anna M. Blom and Joanna H. Webb and Bruno O. Villoutreix and Bj{\"o}rn Dahlb{\"a}ck},
  journal={The Journal of biological chemistry},
  year={1999},
  volume={274 27},
  pages={19237-45}
}
C4b-binding protein (C4BP) is a regulator of the classical complement pathway, acting as a cofactor to factor I in the degradation of C4b. Computer modeling and structural analysis predicted a cluster of positively charged amino acids at the interface between complement control protein modules 1 and 2 of the C4BP alpha-chain to be involved in C4b binding. Three C4BP mutants, R39Q, R64Q/R66Q, and R39Q/R64Q/R66Q, were expressed and assayed for their ability to bind C4b and to function as factor I… CONTINUE READING