Objective: To establish a novel purification method for the rapid purification of Complement Component 5 (C5) based on the affinity of the Staphylococcal Superantigen-Like protein 7 (SSL7) for C5.

Methods: The SSL7 beta grasp domain (7bG) was expressed in E. coli as a soluble fusion protein with thioredoxin. It was isolated by nickel chromatography, cleaved from thioredxin using 3C protease, and further purified using cation exchange. C5 from serum or plasma was pre-cleared of plasminogen using lysine-sepharose, passed over a 7bG-sepharose column and eluted under low pH conditions.

Results: C5 from both human and rabbit was isolated to a high degree of purity using a few simple steps. The C5 eluted from the 7bG-sepharose column was contaminated with small amounts of IgG (presumably anti-SSL7 antibodies) that could be removed with the inclusion of an additional antibody affinity chromatography step. A complement-haemolytic assay was used to confirm that the purified C5 was still functionally active. Using this method C5 could be purified in under 2 days compared with the more traditional purification methods that generally require 4 – 6 days.

Conclusion: In this investigation, a rapid method for the purification of C5 was developed and successfully applied in the purification of human and rabbit C5. C5 purified by this technique is biologically active and can potentially be used in research, diagnostic, or therapeutic applications involving the use of C5.