Regulators Of Complement Activation

Question 1

C1 inhibitor (C1 INH)

Answer 1

Interacts with: C1r, C1s

Function: Binds to C1r and C1s and dissociates them from C1q. This prevents activation and cleavage of C4 or C2

Question 2

Factor I

Answer 2

Interacts with C4b, C3b

Function: cleaves C3b and C4b by using factor H, MCP, C4BP or CR1 as cofactors

Question 3

Factor H

Answer 3

Interacts with: C3b

Function: Binds to C3b and displaces Bb.
Cofactor for factor I- meditated cleavage of C3b

Question 4

C4-binding protein (C4BP)

Answer 4

Interacts with: C4b

Function: Binds to C4b and displaces C2a.
Cofactor for factor I-mediated cleavage of C4b

Question 5

Membrane cofactor for protein (MCP)

Answer 5

Interacts with: C3b, C4b

Function: cofactor for factor I-mediated cleavage of C3b and C4b

Question 6

Decay-accelerating factor (DAF)

Answer 6

Interacts with: C4b2a and C3bBb

Function: Displaces 2a from C4b, and Bb from C3b (dissociation of C3 convertases)

Question 7

CD59

Answer 7

Interacts with: C7, C8

Function: locks C9 binding and prevents formation of the MAC