Production and functional activity of a recombinant von Willebrand factor-A domain from human complement factor B

WILLIAMS, Samantha C.; Hinshelwood, Justin; Perkins, Stephen J.; Sim, Robert B.

doi:10.1042/0264-6021:3420625

Cited by 15 publications

(10 citation statements)

References 11 publications

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“…Thus, the scissile bond in factor B is protected from proteolysis by factor D and is conformationally linked to helices aL and a7. In contrast, the scissile bond in isolated VWA domains is susceptible to factor D cleavage 19 , because they lack the aL-a7 arrangement that locks the P1 residue (Arg234). In the formation of the convertase, binding of C3b to factor B probably induces reshuffling of helices aL and a7 that liberates the P1 arginine residue and makes the scissile bond accessible for proteolysis by factor D.…”

Section: Central Role For Linker Regionmentioning

confidence: 99%

Factor B structure provides insights into activation of the central protease of the complement system

Milder

Gomes

Schouten

et al. 2007

Nat Struct Mol Biol

105

141

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Factor B is the central protease of the complement system of immune defense. Here, we present the crystal structure of human factor B at 2.3-Å resolution, which reveals how the five-domain proenzyme is kept securely inactive. The canonical activation helix of the Von Willebrand factor A (VWA) domain is displaced by a helix from the preceding domain linker. The two helices conformationally link the scissile-activation peptide and the metal ion-dependent adhesion site required for binding of the ligand C3b. The data suggest that C3b binding displaces the three N-terminal control domains and reshuffles the two central helices.Reshuffling of the helices releases the scissile bond for final proteolytic activation and generates a new interface between the VWA domain and the serine protease domain. This allosteric mechanism is crucial for tight regulation of the complementamplification step in the immune response.Factor B is a tightly regulated, highly specific serine protease. In its activated form, it catalyzes the central amplification step of complement activation to initiate inflammatory responses, cell lysis, phagocytosis and B-cell stimulation 1,2 . Factor B is activated through an assembly process: it binds surface-bound C3b, or its fluid-phase counterpart C3(H 2 O), after which it is cleaved by factor D into fragments Ba (residues 1-234) and Bb (residues 235-739) 3,4 . Fragment Ba dissociates from the complex, leaving behind the alternative pathway C3 convertase complex C3b-Bb, which cleaves C3 into C3a and C3b (see Fig. 1a). This protease complex is intrinsically instable. Once dissociated from the complex, Bb cannot reassociate with C3b 5 . A similar C3 convertase complex is formed upon activation of the classical (antibody-mediated) and lectin-binding pathways, comprised of C4 and C2, which are homologous to C3 and factor B, respectively. The proenzyme factor B consists of three N-terminal complement control protein (CCP) domains, connected by a 45-residue linker to a VWA domain and a C-terminal serine protease (SP) domain, which carries the catalytic center (Fig. 1a). The VWA and SP domains form fragment Bb, and CCP1 through CCP3 and the linker form fragment Ba. Binding of factor B to C3b depends on elements in fragment Ba 6 and the Mg 2+ -dependent metal ion-dependent adhesion site (MIDAS) motif in the VWA domain of fragment Bb 7 . The VWA domain is structurally homologous to inserted (I) domains in integrins. In I domains, ligand binding to the MIDAS is coupled to a B10-Å shift of the a7 activation helix, with concomitant domain rearrangements that activate the integrins 8,9 . Structures of a truncated Bb fragment 10 and its full-length homolog C2a 11 show variable positions of the a7 activation helix affecting the orientation of the VWA and SP domains, which indicates that a related mechanism may occur in convertase formation and dissociation. These structures, however, do not reveal the regulation of the proteolytic activity of factor B. In particular, it is unclear how factor B is maintained in its in...

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Section: Central Role For Linker Regionmentioning

confidence: 99%

Factor B structure provides insights into activation of the central protease of the complement system

Milder

Gomes

Schouten

et al. 2007

Nat Struct Mol Biol

105

141

View full text Add to dashboard Cite

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“…Accordingly, the additional cysteine residues, located in the first ␣-helix, may be able to form another disulfide bond, and these unpaired cysteines may be the cause of the aggregation of AMACO, seen under non-reducing conditions. A cysteine residue in a similar position has been described in the VWA domain of complement factor B and leads to dimerization and aggregation of the recombinantly expressed complement factor B VWA domain (28). The two unpaired cysteines in AMACO may form an intramolecular disulfide bond and thereby stabilize the compact, folded structure seen for most of the monomeric AMACO molecules in electron microscopy.…”

Section: Amaco Is Deposited In Extracellular Structures By Transfectementioning

confidence: 99%

Identification and Characterization of AMACO, a New Member of the von Willebrand Factor A-like Domain Protein Superfamily with a Regulated Expression in the Kidney

Sengle

Kobbe

Mörgelin

et al. 2003

Journal of Biological Chemistry

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The genes coding for human and mouse AMACO, an extracellular matrix protein containing VWA-like domains related to those in MAtrilins and COllagens, were detected in databases, the cDNAs were cloned, and the primary structures were deduced from the nucleotide sequences. The genes consist of 14 exons and have a similar exon/intron organization. The protein consists of a signal peptide sequence, an N-terminal VWA domain connected to two additional, tandem VWA domains by a cysteine-rich sequence and an epidermal growth factor (EGF)-like domain. The C terminus is made up of another EGF-like domain followed by a unique sequence present in mouse, but absent in human. The predicted molecular weight of the proteins is 79,485 in human and 83,024 in mouse. Full-length AMACO was expressed in 293-EBNA cells, purified by use of an affinity tag and subjected to biochemical characterization. Both monomers and aggregates of AMACO were recovered, as shown by electron microscopy and SDS-PAGE. AMACO was found in the media of a variety of established cell lines of both fibroblast and epithelial origin. In the matrix formed by 293-EBNA cells overexpressing the protein, AMACO was deposited in patchy structures that were often cell-associated. Affinity-purified antibodies detect expression in cartilage and expression associated with certain basement membranes. In the kidney of adult mice, a second promoter located in intron 4 is active. If the resulting transcript is translated it could not yield a secreted protein because of the lack of a signal peptide sequence. The developmental switch from an AMACO mRNA, expressed by the newborn kidney, to the truncated transcript found in the adult kidney indicates an unusual regulation of AMACO expression.The von Willebrand Factor A-like domain (VWA or vWFA) 1 is a well studied protein module present in a great variety of extracellular proteins, e.g. the prototype von Willebrand factor, the complement factors B and C2, trypsin inhibitors, collagens, matrilins, and integrins. Recently even intracellular members of the protein superfamily have been identified (for review see Ref. 1). It is generally assumed that VWA domains mediate protein-protein interactions and extracellular VWA-domaincontaining proteins are involved in cell-cell, cell-matrix, and matrix-matrix interactions and thereby play roles in important physiological processes such as immunity, hemostasis, and wound healing (2). X-ray crystallography revealed a structure made up from alternating ␣ helices and a central ␤ sheet also known as the Rossman fold. Some VWA domains contain a conserved MIDAS (metal ion-dependent adhesion site) sequence motif, which can be involved in ligand binding. The structures of the A1 domain (3) and the A3 domain (4) of the von Willebrand factor itself, and the VWA domains (I domains) of the integrin ␣ subunits ␣ L (5), ␣ M (2), ␣ 1 (6), ␣ 2 (7), and ␣ V (8), as well as that of the integrin ␤ 3 subunit (8) have been resolved. The binding sites of the vWFA1 domain for Gp1b (9) and those of integrin ␣ 2 (10) ...

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“…BON1 binds to phospholipids in a calcium-dependent manner in vitro, and it is localized to the plasma membrane in plants (Hua et al, 2001). The C-terminal region of BON1 shows homology to the A domain of integrins (Williams et al, 1999) and is proposed to mediate protein-protein interaction, to possess an intrinsic protein kinase activity, or both (Caudell et al, 2000). The A domain in BON1 mediates the interaction of BON1 with its putative functional partner BAP1 that also contains a C2 domain (Hua et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

A Haplotype-Specific Resistance Gene Regulated by BONZAI1 Mediates Temperature-Dependent Growth Control in Arabidopsis

2004

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Plant growth homeostasis and defense responses are regulated by BONZAI1 (BON1), an evolutionarily conserved gene. Here, we show that growth regulation by BON1 is mediated through defense responses. BON1 is a negative regulator of a haplotype-specific Resistance (R) gene SNC1. The bon1-1 loss-of-function mutation activates SNC1, leading to constitutive defense responses and, consequently, reduced cell growth. In addition, a feedback amplification of the SNC1 gene involving salicylic acid is subject to temperature control, accounting for the regulation of growth and defense by temperature in bon1-1 and many other mutants. Thus, plant growth homeostasis involves the regulation of an R gene by BON1 and the intricate interplay between defense responses and temperature responses.

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Production and functional activity of a recombinant von Willebrand factor-A domain from human complement factor B

Cited by 15 publications

References 11 publications

Factor B structure provides insights into activation of the central protease of the complement system

Factor B structure provides insights into activation of the central protease of the complement system

Identification and Characterization of AMACO, a New Member of the von Willebrand Factor A-like Domain Protein Superfamily with a Regulated Expression in the Kidney

A Haplotype-Specific Resistance Gene Regulated by BONZAI1 Mediates Temperature-Dependent Growth Control in Arabidopsis

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