Factor I overexpression 293T lysate (whole cell)

Supplementary information

This supplementary information is collated from multiple sources and compiled automatically.

Factor I also known as Complement Factor I (CFI) is a serine protease involved in the complement system. Its molecular mass is approximately 88 kDa consisting of a heavy and a light chain linked by a disulfide bond. This protein is mainly expressed in the liver and circulates in the plasma. Factor I inhibits the complement pathways by cleaving complement components C3b and C4b preventing the formation of C3 and C5 convertases.

Biological function summary

Factor I plays a role in maintaining immune homeostasis by preventing excessive complement activation. It acts within a complex that includes cofactors such as Factor H Complement Factor 4 binding protein (C4BP) and Membrane Cofactor Protein (MCP). These interactions allow Factor I to selectively degrade activated complement components ensuring that complement activity is kept in check to avoid host cell damage.

Pathways

Factor I operates in both the classical and alternative complement pathways. In the classical pathway it regulates C3b and C4b breakdown to control the formation of the C3 convertase. In the alternative pathway Factor I works in conjunction with Factor H to degrade C3b. This regulation is important to prevent runaway activation protecting healthy tissue from complement-mediated damage.

Factor I deficiencies can lead to conditions like atypical hemolytic uremic syndrome (aHUS) and age-related macular degeneration (AMD). In aHUS insufficient Factor I activity permits unregulated complement activation leading to thrombotic microangiopathy. In AMD aberrant complement activation contributes to retinal damage and degeneration. These conditions illustrate the need for balanced Factor I activity to prevent disease.