3.4.21.47 923DELTADG mutation in complement factor 3 gene identified in patients with dense deposit disease. Mutant C3923DELTADG, which lacks 2 amino acids, cannot be cleaved to C3b by the alternative pathway C3-convertase and is therefore the predominant circulating C3 protein in the patients. Upon activation to C3b by proteases, or to C3(H2O) by spontaneous thioester hydrolysis, mutant C3 generates an active C3-convertase that is regulated normally by decay accelerating factor but is resistant to decay by factor H. Activated C3b923DELTADG and C3(H2O)923DELTADG are resistant to proteolysis by factor I in the presence of factor H, but are efficiently inactivated in the presence of membrane cofactor protein, causing a fluid phase-restricted alternative pathway dysregulation in the patients that continuously activates and consumes C3 produced by the normal C3 allele 717907 3.4.21.47 D254G mutation in the Bb component decreases sensitivity to DAF to 9% of the wild-type value, sensitivity to CR1 to 4% of the wild-type value and sensitivity to Factor H to 48% of the wild-type value 652225 3.4.21.47 D382A mutation in the Bb component decreases sensitivity to DAF to 36% of the wild-type value, sensitivity to CR1 to 41% of the wild-type value 652225 3.4.21.47 D382N mutation in the Bb component decreases sensitivity to DAF to 54% of the wild-type value 652225 3.4.21.47 D445A mutation in the Bb component decreases sensitivity to CR1 to 71% of the wild-type value 652225 3.4.21.47 D715A factor B mutation, severly reduces hemolytic activity, in complex with C3b no cleavage of C3 36600 3.4.21.47 D715E factor B mutation, severly reduces hemolytic activity, in complex with C3b no cleavage of C3 36600 3.4.21.47 D715N factor B mutation, severly reduces hemolytic activity, in complex with C3b no cleavage of C3 36600 3.4.21.47 D715S factor B mutation, severly reduces hemolytic activity 36600 3.4.21.47 D715Y factor B mutation, severly reduces hemolytic activity 36600