scholarly journals Structural and functional studies of complement inhibitor C4b-binding protein

2002 ◽  
Vol 30 (6) ◽  
pp. 978-982 ◽  
Author(s):  
A. M. Blom
Keyword(s):  
Amino Acids ◽  
Computer Modelling ◽  
Binding Protein ◽  
Protein S ◽  
Classical Pathway ◽  
Complement Factor ◽  
Charged Amino Acids ◽  
Α Chain ◽  
Β Chain ◽  
Positively Charged

C4b-binding protein (C4BP) is a potent inhibitor of the classical pathway of the complement system. This large plasma glycoprotein consists of seven identical α-chains and a unique β-chain held together by disulphide bridges. Both types of subunits are composed almost exclusively of complement control protein domains (CCPs). Using homology-based computer modelling and mutagenesis of recombinant proteins we have localized binding sites for several ligands of C4BP: complement factor C4b, heparin and vitamin K-dependent anticoagulant protein S (PS). We found that C4b requires CCP1–3 of the α-chain for binding. The interaction is ionic in nature and mediated by a cluster of positively charged amino acids present on the interface between CCP1 and CCP2 of the α-chain. Loss of C4b-binding resulted in a loss of all inhibitory functions of C4BP within the classical pathway of complement. Binding of heparin required CCPs 1–3 of the α-chain, with CCP2 being the most important, as well as the cluster of positively charged amino acids involved in binding of C4b. The interaction between C4BP and PS is of very high affinity and conveyed by a cluster of surface exposed hydrophobic amino acids localized on CCP1 of the β-chain. Furthermore, C4BP is captured on the surface of several pathogens, which may contribute to their serum resistance and pathogenicity. We have localized interaction of C4BP with Neisseria gonorrhoeae, Bordetella pertussis, Streptococcus pyogenes and Escherichia coli to various regions of the α-chain.

Positively charged amino acids at the interface between α-chain CCP1 and CCP2 of C4BP are required for regulation of the classical C3-convertase

2000 ◽  
Vol 37 (8) ◽  
pp. 445-453 ◽  
Author(s):  
Anna M. Blom ◽  
Anna Foltyn Zadura ◽  
Bruno O. Villoutreix ◽  
Björn Dahlbäck
Keyword(s):  
Amino Acids ◽  
Charged Amino Acids ◽  
Α Chain ◽  
Positively Charged

scholarly journals A Cluster of Positively Charged Amino Acids in the C4BP α-Chain Is Crucial for C4b Binding and Factor I Cofactor Function

1999 ◽  
Vol 274 (27) ◽  
pp. 19237-19245 ◽  
Author(s):  
Anna M. Blom ◽  
Joanna Webb ◽  
Bruno O. Villoutreix ◽  
Björn Dahlbäck
Keyword(s):  
Amino Acids ◽  
Factor I ◽  
Charged Amino Acids ◽  
Α Chain ◽  
Positively Charged

scholarly journals The amino-terminal module of the C4b-binding protein α-chain is crucial for C4b binding and factor I-cofactor function

1997 ◽  
Vol 323 (2) ◽  
pp. 469-475 ◽  
Author(s):  
Ylva HÄRDIG ◽  
Andreas HILLARP ◽  
Björn DAHLBÄCK
Keyword(s):  
Monoclonal Antibodies ◽  
Binding Site ◽  
Binding Protein ◽  
Protein S ◽  
Chimeric Proteins ◽  
Amino Terminal ◽  
Factor I ◽  
Cofactor Activity ◽  
Α Chain ◽  
Β Chain

C4b-binding protein (C4BP) regulates the classical pathway C3-convertase of the complement system. Human C4BP is composed of seven identical subunits (α-chains) and one unique one (β-chain). Both types of chains contain homologous repeats called complement control proteins (CCPs); the α-chain contains eight CCPs and the β-chain three. Each α-chain contains a binding site for C4b although the detailed localization of this binding site is not known. We have used three different chimeric proteins, originally designed to localize the protein S-binding site on C4BP, to demonstrate the importance of the amino-terminal part of the α-chain for the complement-regulatory functions of C4BP. These recombinant proteins were composed of C4BP α-chains with one, two or three of the amino-terminal CCPs replaced by corresponding CCPs from the C4BP β-chain. Furthermore, seven different monoclonal antibodies were raised against C4BP and characterized using the recombinant chimeric proteins. Whereas all three recombinant chimeras bind protein S with the same affinity as plasma-purified C4BP, none of them bound to C4b. Three of the antibodies, which were found to bind to α-chain CCP 1 and CCP 2, completely inhibited the binding of plasma-purified C4BP to immobilized C4b. In addition, two of these antibodies totally blocked the factor I-cofactor activity of C4BP in a C4b-degradation assay. The binding site for one of the monoclonal antibodies was also studied using electron microscopy where it was confirmed that this antibody bound to the amino-terminal tip of the α-chain. These results show that the amino-terminal CCP of the C4BP α-chain (CCP 1) is crucial for the C4b binding and factor I-cofactor activity.

scholarly journals The Superagonistic Activity of Bovine Thyroid-stimulating Hormone (TSH) and the Human TR1401 TSH Analog Is Determined by Specific Amino Acids in the Hinge Region of the Human TSH Receptor

2009 ◽  
Vol 284 (24) ◽  
pp. 16317-16324 ◽  
Author(s):  
Sandra Mueller ◽  
Gunnar Kleinau ◽  
Mariusz W. Szkudlinski ◽  
Holger Jaeschke ◽  
Gerd Krause ◽  
...  
Keyword(s):  
Amino Acids ◽  
Thyroid Stimulating Hormone ◽  
Hinge Region ◽  
Camp Production ◽  
Glycoprotein Hormone ◽  
Charged Amino Acids ◽  
Bovine Thyroid ◽  
Positively Charged ◽  
Bovine Tsh ◽  
Signaling Activity

Bovine TSH (bTSH) has a higher affinity to the human TSHR (hTSHR) and a higher signaling activity than human TSH (hTSH). The molecular reasons for these phenomena are unknown. Distinct negatively charged residues (Glu297, Glu303, and Asp382) in the hinge region of the hTSHR are known to be important for bTSH binding and signaling. To investigate the potential relevance of these positions for differences between bTSH and hTSH in the interaction to the hTSHR, we determined bTSH- and hTSH-mediated cAMP production of several substitutions at these three hinge residues. To examine specific variations of hTSH, we also investigated the superagonistic hTSH analog TR1401 (TR1401), whose sequence differs from hTSH by four additional positively charged amino acids that are also present in bTSH. To characterize possible interactions between the acidic hTSHR positions Glu297, Glu303, or Asp382 and the additional basic residues of TR1401, we investigated TR1401 binding and signaling properties. Our data reveal increased cAMP signaling of the hTSHR using TR1401 and bTSH compared with hTSH. Whereas Asp382 seems to be important for bTSH- and TR1401-mediated but not for hTSH-mediated signaling, the substitution E297K exhibits a decreased signaling for all three TSH variants. Interestingly, bTSH and TR1401 showed only a slightly different binding pattern. These observations imply that specific residues of the hinge region are mediators of the superagonistic activity of bTSH and TR1401 in contrast to hTSH. Moreover, the simultaneous localization of binding components in the glycoprotein hormone molecule and the receptor hinge region permits important reevaluation of interacting hormone receptor domains.

scholarly journals Localization of a Hydrophobic Binding Site for Anticoagulant Protein S on the β-Chain of Complement Regulator C4b-binding Protein

2000 ◽  
Vol 276 (6) ◽  
pp. 4330-4337 ◽  
Author(s):  
Joanna H. Webb ◽  
Bruno O. Villoutreix ◽  
Björn Dahlbäck ◽  
Anna M. Blom
Keyword(s):  
Binding Site ◽  
Binding Protein ◽  
Protein S ◽  
Hydrophobic Binding ◽  
Complement Regulator ◽  
Β Chain

scholarly journals RNA-binding region of Macrobrachium rosenbergii nodavirus capsid protein

2014 ◽  
Vol 95 (9) ◽  
pp. 1919-1928 ◽  
Author(s):  
Zee Hong Goh ◽  
Nur Azmina Syakirin Mohd ◽  
Soon Guan Tan ◽  
Subha Bhassu ◽  
Wen Siang Tan
Keyword(s):  
Amino Acids ◽  
Capsid Protein ◽  
Rna Binding ◽  
Macrobrachium Rosenbergii ◽  
Freshwater Prawn ◽  
Internal Deletion ◽  
Binding Region ◽  
Rna Molecules ◽  
Charged Amino Acids ◽  
Positively Charged

White tail disease (WTD) kills prawn larvae and causes drastic losses to the freshwater prawn (Macrobrachium rosenbergii) industry. The main causative agent of WTD is Macrobrachium rosenbergii nodavirus (MrNV). The N-terminal end of the MrNV capsid protein is very rich in positively charged amino acids and is postulated to interact with RNA molecules. N-terminal and internal deletion mutagenesis revealed that the RNA-binding region is located at positions 20–29, where 80 % of amino acids are positively charged. Substitution of all these positively charged residues with alanine abolished the RNA binding. Mutants without the RNA-binding region still assembled into virus-like particles, suggesting that this region is not a part of the capsid assembly domain. This paper is, to the best of our knowledge, the first to report the specific RNA-binding region of MrNV capsid protein.

scholarly journals A Stretch of Positively Charged Amino Acids at the N Terminus ofHansenula polymorphaPex3p Is Involved in Incorporation of the Protein into the Peroxisomal Membrane

2000 ◽  
Vol 275 (14) ◽  
pp. 9986-9995 ◽  
Author(s):  
Richard J. S. Baerends ◽  
Klaas Nico Faber ◽  
Anita M. Kram ◽  
Jan A. K. W. Kiel ◽  
Ida J. van der Klei ◽  
...  
Keyword(s):  
Amino Acids ◽  
Peroxisomal Membrane ◽  
Charged Amino Acids ◽  
N Terminus ◽  
Positively Charged
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