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	Alternative complement pathway - Wikipedia, the free encyclopedia
		The cascade begins with the spontaneous activation and attachment of the complement protein C3 to a pathogen, creating a catalytic activator that decays both spontaneously and quickly, but can lead to the creation of a C3 convertase.
		The alternative pathway convertase consists of the activated B and D factors, forming an unstable compound that can become stable after binding properdin, a serum protein.
		It is initiated by the spontaneous hydrolysis of C3, which is abundant in the plasma in the blood.
	en.wikipedia.org /wiki/Alternate_complement_pathway (435 words)

	David C. Fritzinger, Ph.D.
		The C3 convertase is subject to regulation by a number of other complement proteins, such as factors H and I, and Complement receptors CR1, CF2, CR3, etc. These proteins serve to regulate complement by either causing dissociation of the C3 convertase or cleaving the active form of C3 to inactivate it.
		Like C3, CVF is able to form a C3 convertase by binding factor B. However, this convertase is several orders of magnitude more stable than the C3 containing enzyme, and is not subject to regulation by other complement proteins.
		-chain) is involved in the binding or cleavage of substrate C3 or C5 molecules, and that the central portion of this chain may be responsible for the stable binding of the enzymatically active portion of the C3 convertase, Bb.
	www.crch.org /ProfileFritzinger.htm (568 words)

	Davidson College: WWW Homepage Template for Biology Students
		C3 is the most abundant protein in the complement system, with a serum concentration of approximately 1.2 mg/mL (Sahu and Lambris, 2001).
		In addition, C3 convertase activity is amplified by factor B in the presence of factor D (Sahu and Lambris, 2001).
		C3 deficiencies inhibit the opsinozation of pathogenic surfaces, limit the chemotaxis of leukocytes to sites of infection, and allow for the survival of pathogens that would normally be destroyed by the membrane-attack complex (e.g.
	www.bio.davidson.edu /Courses/immunology/Students/spring2006/Finley/C3.html (2142 words)

	Alternative pathway (Site not responding. Last check: 2007-09-20)
		Thus, modified C3 has temporarily a greater chance to form the fluid-phase C3 convertase than to become enzymatically degraded by H and I. The function of the initial C3 convertase is to produce metastable C3b and to deposit C3b on the surface of surrounding particles.
		Electron microscopic studies of the C3 convertase have shown that Bb consists of two domains, and that Bb is linked to C3b through only one domain, indicating that this is the binding domain and suggesting that the other may be the C-terminal catalytic domain (52).
		C3b, instead of binding B, binds H and is subsequently cleaved to C3bi (inactivated), therefore H restricts the formation of the C3 convertase and accelerates decay-dissociation of C3bBb (61,62).
	www-micro.msb.le.ac.uk /MBChB/Merralls/Alternative.html (1401 words)

	IDR factfile for C3 deficiency
		C3 gene is structurally related to C4 and alfa macroglobulin.
		C3 deficiency is a rare autosomic recessive inherited disease, characterized by severe recurrent infections and immune-complex disorders.
		C3 deficiency is associated with severe pyogenic infections, glomerulonephritis, and systemic lupus erythematosus.
	dna.uta.fi /xml/idr/FF61.xml (369 words)

	Complement
		Convertase (pronounced CON ver tase) is a general name used for a complement enzyme that converts an inactive complement protein into an active one.
		Many molecules of C3 are cut into C3b, which covalently attaches to the pathogen surface and acts as an opsonin, and C3a, which stimulates inflammation.
		These include plasma proteins C4 binding protein that dissociates classical C3 convertase and Factor H that dissociates alternative C3 convertase, and membrane proteins Complement Receptor 1 (CR1), Decay Accelerating Factor (DAF), and Membrane Cofactor Protein (MCP) that inhibit the activity of both pathways.
	microvet.arizona.edu /Courses/MIC419/Tutorials/complement.html (2288 words)

	Complement
		C4b2a complex, is known as C3 convertase in which C2a is the enzymatic moiety.
		Spontaneous activation of C3 A metastable C3b-like molecule (C3i) is generated by slow hydrolysis of the native C3.
		This C3 convertase (or the one generated by classical pathway: C4b2a), if not inactivated, will continue to act on C3 and cause its total depletion.
	pathmicro.med.sc.edu /ghaffar/complement.htm (1461 words)

	Formation of High-Affinity C5 Convertases of the Alternative Pathway of Complement -- Rawal and Pangburn 166 (4): 2635 ...
		C3 (500 µg) and incubating the cells for 30 min at 22°C. The zymosan particles bearing C3b were washed and the amplification procedure
		For C5 convertases assembled with ZymC3b bearing 31,000 C3b/cell, 38.6 ng of C3b were present in the assay, which resulted in 8.8 nM of enzyme, whereas for those formed with 300,000 C3b/cell ZymC3b, 18.7 ng of C3b were present in the assay resulting in 4.25 nM enzyme.
		C5 convertase of the alternative pathway of complement: kinetic analysis of the free and surface-bound forms of the enzyme.
	www.jimmunol.org /cgi/content/full/166/4/2635 (5771 words)

	C3 is THE key component of Complement
		In native C3 this bond is stable but this thiolester bond can become highly reactive as a result of conformational changes in the C3 protein structure.
		C4 and C3 are homologous as are C2 and factor B. The C3 convertases are powerful amplifiers of complement activation, up to 1000 C3 molecules are cleaved to C3b by each molecule of active C3 convertase.
		Each C3 convertase can be converted into a C5 convertase by the binding of a C3b molecule; this subsequently splits C5 into C5b and C5a.
	www.cartage.org.lb /en/themes/sciences/LifeScience/GeneralBiology/Immunology/ComplementSystem/C3/C3.htm (536 words)

	Chicken Anti-C3 Polyclonal Antibody, Unconjugated from GeneTex - Biocompare Buyer's Guide
		Chicken polyclonal to C3 The complement factor C3 consists of an alpha and a beta chain.
		C3 is a central factor in the complement cascade.
		C3 is an acute phase protein that is produced by a wide range of tissues, including renal epithelial cells and hepatocytes.
	www.biocompare.com /itemdetails.asp?itemid=367357 (155 words)

	Complementary Recognition of Alternative Pathway Activators by Decay-Accelerating Factor and Factor H -- Kraus et al. ...
		C3 deposition by purified C3, B, and D in the absence of regulatory proteins was nearly equal for all liposome types (data
		to form the ACP C3 convertase in the presence and absence of H. Inhibition of convertase activity by H was determined as the percent decrease in bound
		DAF inhibits the assembly of C3 convertases by dissociating C2a and Bb.
	iai.asm.org /cgi/content/full/66/2/399 (5114 words)

	C3 (complement) - Wikipedia, the free encyclopedia
		In immunology, soluble C3-convertase, also known as iC3Bb, catalyzes the proteolytic cleavage of C3 into C3a and C3b as part of the alternative complement system.
		Also know as C3bBb, this convertase similar to soluble C3-convertase except that it is membrane bound.
		Alternatively, binded C3b may aid in opsonization of the microbe by macrophages.
	en.wikipedia.org /wiki/C3_(complement) (144 words)

	Bacterial Killing
		C3b binds because during activation of C3 a thiol bond is exposed which permits the formation of ester or amide bonds (covalent binding) with the bacterial surface structures.
		C3 is activated by limited proteolysis by enzymes called C3 convertases.
		There are two C3 convertases, one produced by activation of the classical pathway which is antibody dependent (IgM or IgG), while the alternative pathway can be activated in the absence of antibody.
	www-micro.msb.le.ac.uk /MBChB/4a.html (573 words)

	Inhibition of the alternative C3 convertase and classical C5 convertase of complement by group A streptococcal M ...
		Inhibition of the alternative C3 convertase and classical C5 convertase of complement by group A streptococcal M protein.
		When M+ and M- streptococci were incubated with normal human serum containing radiolabeled C3 in the presence of Ca2+ and Mg2+, more than 85% of the C3 bound to either type of streptococcus was extractable by sodium dodecyl sulfate and alkali treatment.
		These results support and extend previous findings that the antiphagocytic activity of streptococcal M protein may be due to complement inhibition mediated by the binding of factor H. Pretreatment of M+ bacteria with the Fab fragment of rabbit immunoglobulin G anti-M antibody also increased their binding of C3 in the absence of Ca2+.
	www.ihop-net.org /UniPub/iHOP/gp/13976.html (300 words)

	Human Factor H-Related Protein 5 Has Cofactor Activity, Inhibits C3 Convertase Activity, Binds Heparin and C-Reactive ...
		convertase was not observed in a solid phase assay.
		Inhibition of C3 convertase was determined by C3a generation after 30 min of incubation and measured by a C3a ELISA.
		Generation of the C3bBb(Ni) complex (alternative pathway C3 convertase) was achieved by addition of factor B, factor D, and properdin in the presence of NiCl
	www.jimmunol.org /cgi/content/full/174/10/6250 (5417 words)

	How Complement Works
		What remains bound to the membrane is C4b2a, also known as the C3 convertase because its role is to convert the next complement component, C3, into its active form.
		The C5 convertase, much like the C3 convertase before it, catalyzes the cleavage of hundreds to thousands of C5 complement component into C5a and C5b before it reverts to inactivity.
		The C3 convertase of the alternative pathway is, however, not particularly stable.
	www.brown.edu /Courses/Bio_160/Projects1999/ies/how.html (1409 words)

	GeneCard for C3
		C3 convertase activates C3 by cleaving the alpha chain,
		Its processing by C3 convertase is the central reaction in both classical and alternative complement pathways.
		Function: Derived from proteolytic degradation of complement C3, C3a anaphylatoxin is a mediator of
	www.genecards.org /cgi-bin/carddisp.pl?gene=C3 (538 words)

	Decay-accelerating Factor (DAF), Complement Receptor 1 (CR1), and Factor H Dissociate the Complement AP C3 Convertase ...
		The AP C3 convertase is assembled in two steps.
		Activation of human C3 is regulated by a family of related proteins termed the regulators of complement activation (RCA) (5-7).
		The C3 convertases are the central amplification enzymes of the complement cascade, and their proper regulation is essential
	www.jbc.org /cgi/content/full/277/2/1107 (4096 words)

	Anti-C3 , C3 , C3 antibody
		Its activation by a C3 convertase releases the C3a anaphylatoxin from the amino end of the alpha chain and generates C3b, which associates with the Bb fragment of complement factor B to form the alternative-complement-pathway C3/C5 convertase.C3a anaphylatoxin is a vasoactive peptide and a mediator of inflammation.
		C3b, with its highly reactive thiol group, binds to the surface of foreign particles and facilitates phagocytosis.
		It binds to complement C5 and renders it susceptible to proteolysis by the classical-complement-pathway C3/C5 convertase.
	www.prosci-inc.com /Antibody-XW-TDS/XW-7061.html (189 words)

	Mutants of Complement Component C3 Cleaved by the C4-Specific C1s Protease -- Mathias et al. 89 (17): 8125 -- ... (Site not responding. Last check: 2007-09-20)
		To identify some of the structural features determining specific protease recognition of complement components C3 and C4, we used site-specific mutagenesis to construct mutants of murine C3 that are cleaved by the C4-specific C 1s protease.
		Insertion of three amino acid residues corresponding to residues at the C 1s cleavage site of human C4 into murine C3 at the analogous C3 convertase cleavage site was adequate to render the mutant protein susceptible to C 1s cleavage.
		A simple interpretation of these data is that C 1s cleavage is dependent primarily on steric accessibility and on recognition of specific amino acid residues at the cleavage site, whereas C3 convertase cleavage is dependent primarily on specific interactions distal to the cleavage site, with only relatively weak, non-C3-specific interactions at the cleavage site itself.
	intl.pnas.org /cgi/content/abstract/89/17/8125 (445 words)

	ETH - Biochemistry - NAbs regulating complement amplification
		The C3b2-IgG complexes are very efficient precursors of the alternative pathway C3 convertase, because C3b in C3b2-IgG complexes is structurally partially protected from inactivation and therefore has a longer half life than free C3b.
		Nephritic factors are pathologic autoaggressive antibodies that bind to the assembled C3 convertase and slow down its decay.
		The C3 convertase functional assay was further developed to allow studying the precursor stability and C3 convertase assembly in the presence of IgG NAbs.
	www.mol.biol.ethz.ch /IBC/people/groups/lutzh/research/nabs (569 words)

	Properdin- and nephritic factor-dependent C3 convertases: requirement of native C3 for enzyme formation and the ...
		Properdin- and nephritic factor-dependent C3 convertases: requirement of native C3 for enzyme formation and the function of bound C3b as properdin receptor -- Schreiber et al.
		Properdin- and nephritic factor-dependent C3 convertases: requirement of native C3 for enzyme formation and the function of bound C3b as properdin receptor
		utilize native C3 instead of C3b and PA in an apparently uncleaved form.
	www.jem.org /cgi/content/abstract/142/3/760 (305 words)

	Formation of the initial C3 convertase of the alternative complement pathway. Acquisition of C3b-like activities by ...
		Formation of the initial C3 convertase of the alternative complement pathway.
		Unlike native C3, C3 bearing a single reactive sulfhydryl group was capable of generating
		fluid-phase C3 convertase with Factors B, D, and P and was cleaved by
	www.jem.org /cgi/content/abstract/154/3/856 (585 words)

	Persistently circulating C3 nephritic factor (C3 NeF)-stabilized alternative pathway C3 convertase (C3 CoF) in serum of ... (Site not responding. Last check: 2007-09-20)
		Persistently circulating C3 nephritic factor (C3 NeF)-stabilized alternative pathway C3 convertase (C3 CoF) in serum of an 11-year-old girl with meningococcal septicemia--simultaneous occurrence with free C3 NeF -- Wahn et al.
		Persistently circulating C3 nephritic factor (C3 NeF)-stabilized alternative pathway C3 convertase (C3 CoF) in serum of an 11-year-old girl with meningococcal septicemia--simultaneous occurrence with free C3 NeF
		The factor responsible for this phenomenon was termed C3 converting factor
	www.pedresearch.org /cgi/content/abstract/22/2/123 (368 words)

	ETH - Biochemistry - Projects
		Modulation of the alternative pathway C3 convertase formation and stability by naturally occurring antibodies
		We will characterize the puriifed NAbs and study their functional properties using the C3 convertase assay.
		We characterize the NAbs eluted from such RBC and study the plasma content for the same NAbs, to find out whether a positive Coombs test in healthy blood donors is induced by changes in the NAb repertoire.
	www.mol.biol.ethz.ch /IBC/people/groups/lutzh/research/nabs/projects (773 words)

	Formation of High Affinity C5 Convertase of the Classical Pathway of Complement -- Rawal and Pangburn 278 (40): 38476 ...
		Formation of High Affinity C5 Convertase of the Classical Pathway of Complement -- Rawal and Pangburn 278 (40): 38476 -- Journal of Biological Chemistry
		C3/C5 convertase is a serine protease that cleaves C3 and C5.
		cleave C3 opsonizing the cell surface with C3b for phagocytosis.
	www.jbc.org /cgi/content/abstract/278/40/38476 (448 words)

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