Information on EC 3.4.21.47 - alternative-complement-pathway C3/C5 convertase

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The enzyme appears in viruses and cellular organisms

EC NUMBER
COMMENTARY hide
3.4.21.47
-
RECOMMENDED NAME
GeneOntology No.
alternative-complement-pathway C3/C5 convertase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
Cleavage of Arg-/-Ser bond in complement component C3 alpha-chain to yield C3a and C3b, and Arg-/- bond in complement component C5 alpha-chain to yield C5a and C5b
show the reaction diagram
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
hydrolysis of peptide bond
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endopeptidase
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CAS REGISTRY NUMBER
COMMENTARY hide
80295-67-6
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
-
-
-
Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
metabolism
physiological function
additional information
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
complement component C3 + H2O
complement component C3a + complement component C3b
show the reaction diagram
complement component C3 zymogen + H2O
complement component C3b + complement component C3a
show the reaction diagram
complement component C5 + H2O
complement component C5a + complement component C5b
show the reaction diagram
complement component C5 zymogen + H2O
complement component C5b + complement component C5a
show the reaction diagram
t-butyloxycarbonyl-Gly-L-Leu-L-Ala-L-Arg-thiobenzyl ester
?
show the reaction diagram
substrate of enzyme subunit Bb
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-
?
tert-butoxycarbonyl-Leu-Gly-Arg-7-amido-4-methylcoumarin + H2O
tert-butoxycarbonyl-Leu-Gly-Arg + 7-amino-4-methylcoumarin
show the reaction diagram
-
-
-
?
tert-butoxycarbonyl-norleucine-Gln-Leu-Gly-Arg-7-amido-4-methylcoumarin + H2O
tert-butoxycarbonyl-norleucine-Gln-Leu-Gly-Arg + 7-amino-4-methylcoumarin
show the reaction diagram
-
-
-
?
additional information
?
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
complement component C3 + H2O
complement component C3a + complement component C3b
show the reaction diagram
complement component C3 zymogen + H2O
complement component C3b + complement component C3a
show the reaction diagram
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activation
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-
?
complement component C5 + H2O
complement component C5a + complement component C5b
show the reaction diagram
complement component C5 zymogen + H2O
complement component C5b + complement component C5a
show the reaction diagram
-
activation
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-
?
additional information
?
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Ni2+
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promotes a stable C3bB complex
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
6-amidino-2-naphthyl-4-guanidinobenzoate
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-
Ab (2B7)
inhibits the deposition of C3b on Escherichia coli in hemolymph plasma, whereas it exhibits no inhibitory effect on the deposition of C3b on Staphylococcus aureus
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Aurin tricarboxylic acid
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blocks the alternative pathway at a downstream step from C3b attachment. It prevents formation of C3 convertase at the stage where Factor B, attached to the membrane-bound properdin-C3b-Factor B (PC3bB) complex, is cleaved by the protease action of Factor D to form the active C3 convertase enzyme PC3bBb. Activity is restored by the addition of excess Factor D to the serum. But membrane attack complex formation is still blocked by ATA at the stage of C9 addition to C5b678. It has no effect on the classical pathway activation. Binding of aurin tricarboxylic acid to the QPDTIDHDLLLLQLS site blocks the ability of aurin tricarboxylic acid to bind to Factor D protein
C3b-specific antibody fragment S77
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inhibits the alternative pathway C5 convertase in human serum
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complement factor H-related protein 1
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0.005-0.16 mg/ml inhibits C5 convertase activity
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complement receptor 1
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CR1, mediates decay acceleration of the C3bBb complex
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CRIg
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phagocytic receptor, binds to the beta-chain of complement components C3b and C3c and inhibits the AP C3 and C5 convertases, structure-activity relationship of CRIg mutants indicated
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decay accelerating factor
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DAF, mediates decay acceleration of the C3bBb complex
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decay-accelerating factor
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DAF, CD55, major site of interaction with the larger cleavage subunit complement component factor B (Bb), interaction pathway dissected, second short consensus repeat (SCR) domain of DAF (SCR2) interacts only with fragment Bb, whereas SCR4 interacts with complement component C3b, SCR3 does not directly interact with either subunit
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Diisopropyl phosphate
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factor H
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hemocyanin-depleted plasma
preincubation of hemocyanin-depleted plasma with the anti-factor C Ab (2B7) dose-dependently inhibits the proteolytic conversion of C3 to C3b in the presence of LPS
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hydroxylamine
inactivates the thioester bond on C3, dramatically decreases the deposition of C3b on microbes
Leu-Gly-Leu-Ala-Arg-sarcosine
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inhibits C5 cleavage
OmCI
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the inhibitor blocks C5 cleavage by interfering with convertase recognition far from C5a
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Pra1
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i. e. Candida albicans complement regulator acquiring surface protein 2 or pH-regulated Ag 1. In the direct surrounding of the pathogen, inhibitor binds to fluid-phase C3, blocks cleavage of C3 to C3a and C3b and inhibits complement activation via the alternative and classical pathways. In addition, the release of the anaphylatoxins C3a and C5a, as well as C3b/iC3b surface deposition, is reduced. By reducing C3b/iC3b levels at the yeast surface, Pra1 decreases complement-mediated adhesion, as well as uptake of Candida albicans by human macrophages
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SSL7
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the inhibitor blocks C5 cleavage by interfering with convertase recognition far from C5a
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staphylococcal complement inhibitor
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thioredoxin 1
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Trx-1, causes significant inhibition of alternative convertases, mechanism, overview. Trx-1 is capable of inhibiting all classical and alternative convertases but its effect is more pronounced in inhibition of alternative ones
TT30
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therapeutic fusion protein linking the human complement receptor type 2 C3 fragment-binding domain with the CAP inhibitory domain of human factor H. TT30 efficiently blocks ex vivo CAP-dependent accumulation of C3-fragment on activated surfaces, membrane attack complex formation and hemolysis of red blood cells, without interference of C3 activation or membrane attack complex formation
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additional information
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
factor B
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factor C
acts as an LPS-responsive C3 convertase on the surface of invading Gram-negative bacteria in the initial phase of horseshoe crab complement activation. The proteolytic activity of factor C on the surface of Escherichia coli is essential for the deposition of C3b
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factor D
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formyl-methionyl-leucylphenylalanine
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treatment of whole blood leads to stimulation of neutrophils resulting in activation of the alternative complement pathway and release of C5 fragments, which further amplify proinflammatory responses
human complement factor H-related protein 4
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CFHR 4, two isozymes A and B of 86 and 45 kDa from plasma, domain structure, overview. The protein belongs to the factor H family of plasma glycoproteins that are composed of short consensus repeat (SCR) domains. It activates complement by serving as a platform for the assembly of alternative pathway C3 convertase via its interaction with C3b protein. CFHR4 binds C3b via its C-terminus, and it lacks SCRs homologous to the complement inhibitory domains of factor H and has no significant complement regulatory activities. In contrast to the complement inhibitor factor H, CFHR4 acts as an enhancer of opsonization by promoting complement activation
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LPS
proteolytic conversion of C3 to C3b in hemocyanin-depleted plasma is strongly induced by LPS
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mannan-binding lectin
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phorbol myristate acetate
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treatment of whole blood leads to stimulation of neutrophils resulting in activation of the alternative complement pathway and release of C5 fragments, which further amplify proinflammatory responses
properdin
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tumor necrosis factor-alpha
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treatment of whole blood leads to stimulation of neutrophils resulting in activation of the alternative complement pathway and release of C5 fragments, which further amplify proinflammatory responses
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zymosan
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it is capable of activating the classical pathway as well as the alternative pathway, when the classical pathway is blocked, mechanism, overview
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additional information
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.00586 - 0.0264
complement component C3
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0.0000075 - 0.0688
Complement component C5
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2.75 - 5.63
t-butyloxycarbonyl-Gly-L-Leu-L-Ala-L-Arg-thiobenzyl ester
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.107 - 1.78
complement component C3
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0.0038 - 0.026
Complement component C5
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0.28 - 0.65
t-butyloxycarbonyl-Gly-L-Leu-L-Ala-L-Arg-thiobenzyl ester
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
7.3
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assay at
7.4
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assay at
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
37
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assay at
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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contains factor B
Manually annotated by BRENDA team
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
-
-
-
Manually annotated by BRENDA team
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
185000
x * 185000, SDS-PAGE
200000
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x * 200000, enzyme component C3, SDS-PAGE
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
POSTTRANSLATIONAL MODIFICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
proteolytic modification
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association of factor B with C3b in the presence of Mg2+ results in the formation of a bimolecular zymogen C3b,B, which is activated by the serine proteinase factor D, generating the C3 convertase, C3b,Bb
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
C3 convertase formed by C3b and the protease fragment Bb in complex with staphylococcal complement inhibitor, hanging drop vapor diffusion method, using 75 mM sodium/potassium tartrate, 8.0% (w/v) PEG 3350, 50 mM Bis-Tris propane, pH 6.5
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crystal structures of the pro-convertase C3bB at 4 A resolution and its complex with factor D at 3.5 A resolution. Factor B binding to C3b forms an open activation state of C3bB. Factor D specifically binds the open conformation of factor B through a site distant from the catalytic center and is activated by the substrate, which displaces factor D’s self-inhibitory loop. This concerted proteolytic mechanism, which is cofactordependent and substrate-induced, restricts complement amplification to C3b-tagged target cells
engineered subunit Bb with Cys-resiudes at positions 435 and 428, in complex with inhibitors 6-amidino-2-naphthyl-4-guanidinobenzoate or diisopropyl phosphate
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in complex with factor H, hanging drop vapor diffusion method, using 7.0% (w/v) PEG 3350, 70 mM ammonium acetate, pH 7.1, at 18°C
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structural analysis of complement component C3b in complex with the macrophage-expressed complement receptor CRIg, domain architecture of complement component C3 and the C3b/C3c-CRIg complexes shown, structural similarities between complement components C3b and C3c indicated, comparison between complement components C3b and C3 reveals that complement component C3 stimulation is accompanied by major strucural rearrangements
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TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
marked stabilization of enzyme by naturally occuring IgG directed against the enzyme. Antibody prevents convertase decay in the presence of factor H. In addition, the antibody stabilizes enzyme precursors and promotes enzyme assembly
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properdin stabilizes enzyme-IgG complexes before any other complement protein has bound to them. The alternative pathway of convertase generation may depend on whether properdin is bound to its precursor, a C3b or a C3b2-IgG complex
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the C3 convertase is stabilized by the binding of properdin
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the enzyme has a very short half-life. Dissociation of the two noncovalently bound subunits proceeds with a half-life of 1-3 min at 37°C under physiological conditions, and this rate increases greatly if regulatory proteins are present. Numerous decay-accelerating proteins are present in plasma and on host cells that bind to the noncatalytic subunit C3b and increase the rate at which the catalytic subunit Bb is released into the medium. Bb loses its enzymatic activity and its ability to bind to C3b upon release. Although C3b is able to rebind Bb and reform the enzyme, the interaction with most decay-accelerating factors also leads to permanent proteolytic interaction of the cell-bound subunit C3b by a fluid-phase protease Factor I. These regulatory events limit cleavage of C3, reduce release of the anaphylatoxin C3a and control the formation of more efficient C5 convertase enzymes
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the enzyme is subject to irreversible dissociation by three proteins: DAF, CR1 and factor H
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
affinity purification of factor B
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by ion-exchange chromatography
C3bB(Ni2+) complex or C3bBb(factor B-D279G mutant) purified by gel filtration
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complement proteins purified by gel filtration, to homogeneity
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magnetic cobalt beads chromatography and analytical ultracentrifugation
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
factor B, expression in COS cells
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
Streptococcus pneumoniae induces increased gene expression of factor B of the alternative complement pathway and C3 in mouse middle ear epithelium. Activation of factor B and C3 in the middle ear lavage fluids is significantly greater than in simultaneously obtained serum samples
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
923DELTADG
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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
D254G
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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
D382A
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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
D382N
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mutation in the Bb component decreases sensitivity to DAF to 54% of the wild-type value
D445A
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mutation in the Bb component decreases sensitivity to CR1 to 71% of the wild-type value
D715A
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factor B mutation, severly reduces hemolytic activity, in complex with C3b no cleavage of C3
D715E
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factor B mutation, severly reduces hemolytic activity, in complex with C3b no cleavage of C3
D715N
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factor B mutation, severly reduces hemolytic activity, in complex with C3b no cleavage of C3
D715S
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factor B mutation, severly reduces hemolytic activity
D715Y
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factor B mutation, severly reduces hemolytic activity
E207A
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mutation in proenzyme factor B. Mutation disrupts salt bridge R234-E207, with little effects on the cleavage of proenzyme factor B
E301A
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mutation in the Bb component decreases sensitivity to DAF to 75% of the wild-type value
E316A
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mutation in the Bb component decreases sensitivity to DAF to 71% of the wild-type value
E379A
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mutation in the Bb component decreases sensitivity to DAF to 52% of the wild-type value, sensitivity to CR1 to 50% of the wild-type value
E434A
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mutation in the Bb component decreases sensitivity to CR1 to 65% of the wild-type value
E446V
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mutation in proenzyme factor B. Mutation disrupts salt bridge R234-E446 which partly stabilizes the complex C3bB(Mg2+) thereby inhibiting activation of the proenzyme
F716A
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factor B mutation, severly reduces hemolytic activity
K265A/K266A
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Mutation in the Bb component decreases sensitivity to DAF to 18% of the wild-type value, sensitivity to CR1 to 18% of the wild-type value and sensitivity to Factor H to 19% of the wild-type value
K294A
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mutation in the Bb component decreases sensitivity to CR1 to 44% of the wild-type value
M341A
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mutation in the Bb component decreases sensitivity to Factor H to 75% of the wild-type value
N260D
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mutation in the Bb component decreases sensitivity to DAF to 32% of the wild-type value, sensitivity to CR1 to 31% of the wild-type value and sensitivity to Factor H to 24% of the wild-type value
Q335A
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mutation in the Bb component decreases sensitivity to DAF to 20% of the wild-type value
S339A
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mutation in the Bb component decreases sensitivity to DAF to 32% of the wild-type value, sensitivity to CR1 to 50% of the wild-type value
W343A
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mutation in the Bb component decreases sensitivity to DAF to 55% of the wild-type value, sensitivity to CR1 to 56% of the wild-type value
Y338A
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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
Y338F
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mutation in the Bb component decreases sensitivity to DAF to 18% of the wild-type value, sensitivity to CR1 to 20% of the wild-type value and sensitivity to Factor H to 61% of the wild-type value
Y338S
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mutation in the Bb component decreases sensitivity to DAF to 5% of the wild-type value, sensitivity to CR1 to 24% of the wild-type value
additional information
APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
medicine