scholarly journals Structure of complement C3(H2O) revealed by quantitative cross-linking/mass spectrometry and modeling

2016 ◽  
Author(s):  
Zhuo A. Chen ◽  
Riccardo Pellarin ◽  
Lutz Fischer ◽  
Andrej Sali ◽  
Michael Nilges ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
3D Model ◽  
Domain Architecture ◽  
Factor H ◽  
Complement C3 ◽  
Cross Linking ◽  
First Line ◽  
Structural Differences ◽  
The Complement System

AbstractThe slow but spontaneous and ubiquitous formation of C3(H2O), the hydrolytic and conformationally rearranged product of C3, initiates antibody-independent activation of the complement system that is a key first line of antimicrobial defense. The structure of C3(H2O) has not been determined. Here we subjected C3(H2O) to quantitative cross-linking/mass spectrometry (QCLMS). This revealed details of the structural differences and similarities between C3(H2O) and C3, as well as between C3(H2O) and its pivotal proteolytic cleavage product, C3b, which shares functionally similarity with C3(H2O). Considered in combination with the crystal structures of C3 and C3b, the QCMLS data suggest that C3(H2O) generation is accompanied by the migration of the thioester-containing domain of C3 from one end of the molecule to the other. This creates a stable C3b-like platform able to bind the zymogen, factor B, or the regulator, factor H. Integration of available crystallographic and QCLMS data allowed the determination of a 3D model of the C3(H2O) domain architecture. The unique arrangement of domains thus observed in C3(H2O), which retains the anaphylatoxin domain (that is excised when C3 is enzymatically activated to C3b), can be used to rationalize observed differences between C3(H2O) and C3b in terms of complement activation and regulation.

scholarly journals Hijacking Factor H for Complement Immune Evasion

2021 ◽  
Vol 12 ◽  
Author(s):  
Sara R. Moore ◽  
Smrithi S. Menon ◽  
Claudio Cortes ◽  
Viviana P. Ferreira
Keyword(s):  
Host Cell ◽  
Complement System ◽  
Alternative Pathway ◽  
Expression Patterns ◽  
Fluid Phase ◽  
Factor H ◽  
Host Cells ◽  
Complement C3 ◽  
Complement Regulators ◽  
The Complement System

The complement system is an essential player in innate and adaptive immunity. It consists of three pathways (alternative, classical, and lectin) that initiate either spontaneously (alternative) or in response to danger (all pathways). Complement leads to numerous outcomes detrimental to invaders, including direct killing by formation of the pore-forming membrane attack complex, recruitment of immune cells to sites of invasion, facilitation of phagocytosis, and enhancement of cellular immune responses. Pathogens must overcome the complement system to survive in the host. A common strategy used by pathogens to evade complement is hijacking host complement regulators. Complement regulators prevent attack of host cells and include a collection of membrane-bound and fluid phase proteins. Factor H (FH), a fluid phase complement regulatory protein, controls the alternative pathway (AP) both in the fluid phase of the human body and on cell surfaces. In order to prevent complement activation and amplification on host cells and tissues, FH recognizes host cell-specific polyanionic markers in combination with complement C3 fragments. FH suppresses AP complement-mediated attack by accelerating decay of convertases and by helping to inactivate C3 fragments on host cells. Pathogens, most of which do not have polyanionic markers, are not recognized by FH. Numerous pathogens, including certain bacteria, viruses, protozoa, helminths, and fungi, can recruit FH to protect themselves against host-mediated complement attack, using either specific receptors and/or molecular mimicry to appear more like a host cell. This review will explore pathogen complement evasion mechanisms involving FH recruitment with an emphasis on: (a) characterizing the structural properties and expression patterns of pathogen FH binding proteins, as well as other strategies used by pathogens to capture FH; (b) classifying domains of FH important in pathogen interaction; and (c) discussing existing and potential treatment strategies that target FH interactions with pathogens. Overall, many pathogens use FH to avoid complement attack and appreciating the commonalities across these diverse microorganisms deepens the understanding of complement in microbiology.

scholarly journals Structure of Complement C3(H2O) Revealed By Quantitative Cross-Linking/Mass Spectrometry And Modeling

2016 ◽  
Vol 15 (8) ◽  
pp. 2730-2743 ◽  
Author(s):  
Zhuo A. Chen ◽  
Riccardo Pellarin ◽  
Lutz Fischer ◽  
Andrej Sali ◽  
Michael Nilges ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Complement C3 ◽  
Cross Linking

scholarly journals Lysine and Arginine Side Chains in Glycosaminoglycan−Protein Complexes Investigated by NMR, Cross-Linking, and Mass Spectrometry: A Case Study of the Factor H−Heparin Interaction

2010 ◽  
Vol 132 (18) ◽  
pp. 6374-6381 ◽  
Author(s):  
Bärbel S. Blaum ◽  
Jon A. Deakin ◽  
Conny M. Johansson ◽  
Andrew P. Herbert ◽  
Paul N. Barlow ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Protein Complexes ◽  
Factor H ◽  
Cross Linking ◽  
Side Chains ◽  
Heparin Interaction

scholarly journals Quantitative cross-linking/mass spectrometry reveals subtle protein conformational changes

2016 ◽  
Vol 1 ◽  
pp. 5 ◽  
Author(s):  
Zhuo Chen ◽  
Lutz Fischer ◽  
Salman Tahir ◽  
Jimi-Carlo Bukowski-Wills ◽  
Paul Barlow ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Conformational Changes ◽  
Complement C3 ◽  
Cross Linking ◽  
Complement Protein ◽  
Protein Protein Interaction ◽  
Code Of Practice ◽  
Final Maturation ◽  
Cross Links ◽  
Binary Switching

Quantitative cross-linking/mass spectrometry (QCLMS) probes protein structural dynamics in solution by quantitatively comparing the yields of cross-links between different conformational statuses. We have used QCLMS to understand the final maturation step of the proteasome lid and also to elucidate the structure of complement C3(H2O). Here we benchmark our workflow using a structurally well-described reference system, the human complement protein C3 and its activated cleavage product C3b. We found that small local conformational changes affect the yields of cross-linking residues that are near in space while larger conformational changes affect the detectability of cross-links. Distinguishing between minor and major changes required robust analysis based on replica analysis and a label-swapping procedure. By providing workflow, code of practice and a framework for semi-automated data processing, we lay the foundation for QCLMS as a tool to monitor the domain choreography that drives binary switching in many protein-protein interaction networks.

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