Proteases of the complement system.

  title={Proteases of the complement system.},
  author={Robert B Sim and Stefanos A Tsiftsoglou},
  journal={Biochemical Society transactions},
  volume={32 Pt 1},
The complement system is a group of about 35 soluble and cell-surface proteins which interact to recognize, opsonize and clear or kill invading micro-organisms or altered host cells (e.g. apoptotic or necrotic cells). Complement is a major part of the innate immune system. Recognition proteins such as C1q, MBL (mannan-binding lectin) and ficolins bind to targets via charge or sugar arrays. Binding causes activation of a series of serine protease proenzymes, such as C1r, C1s and MASP2 (MBL… 
Complement Protease C1r
The complement system plays a major role in natural resistance to bacterial and viral infections, and is equipped with soluble and membrane regulatory proteins that target their inhibitory activity at three key steps in complement activation.
Serine Proteases in the Lectin Pathway of the Complement System
The complement system plays a crucial role in host defense against pathogen infections and in the recognition and removal of damaged or altered self-components. Complement system activation can be
Analogous Interactions in Initiating Complexes of the Classical and Lectin Pathways of Complement1
This work has analyzed binding between human C1q, C1r, and C1s, which associate to form C1, using full-length and truncated protease components and proposes a new model using mannan-binding Lectin-mannan-binding lectin-associated serine protease interactions as a template.
Complement Proteins as Soluble Pattern Recognition Receptors for Pathogenic Viruses
This review focuses on complement-dependent and -independent interactions of complement components (especially C1q, C4b-binding protein, properdin, factor H, Mannose-binding lectin, and Ficolins) with several viruses and their consequences.
Mannose-binding lectin serine proteases and associated proteins of the lectin pathway of complement: two genes, five proteins and many functions?
The proteases form an interesting sub-family of proteins that clearly should be the focus of future research in order to establish their biological roles and be able to augment MASP-2 activation, but also appears to play other roles, although the physiological significance of these is not yet clear.
Elucidation of the substrate specificity of the MASP-2 protease of the lectin complement pathway and identification of the enzyme as a major physiological target of the serpin, C1-inhibitor.
The cleavage specificity of MASP-2 is elucidated using a randomised substrate phage display library and it is shown that the crucial P1 position plays the greatest role in determining specificity, with Gly residues preferred at P2 and Leu or hydrophobic residues at P3.
Interactions between mannose-binding lectin and MASPs during complement activation by the lectin pathway
The lectin pathway of complement performs a key role within the immune system by recognising pathogens through patterns of sugar moieties displayed on their cell surfaces and neutralising them via an
Engineering Novel Complement Activity into a Pulmonary Surfactant Protein*
Novel complement activity is introduced concurrently with MASP binding in SP-A but is uncontrolled and occurs even in the absence of a carbohydrate target, meaning the active rather than the zymogen state is default in lectin·MASP complexes and must be inhibited through additional regions in circulating MBLs until triggered by pathogen recognition.
Structural biology of the membrane attack complex.
Recent structures of MAC components and homologous proteins significantly increased the understanding of oligomerisation, membrane association and integration, shedding light onto the molecular mechanism of this important branch of the innate immune system.
Multiple domains of MASP-2, an initiating complement protease, are required for interaction with its substrate C4.
It is shown that both proteolytically active and catalytically inactive CCP1-CCP2-serine protease forms bind C4 with similar affinity, and that all of the domains are required in order to mediate high affinity interaction with C4.


The Complement Factsbook
Abbreviations. Preface. Section 1: The Introductory Chapters B.J. Morley and M. Walport, Introduction. B.J. Morely and M. Walport, The Complement System. Section II: The Complement Proteins Part 1:
Complement, A Practical Approach (Dodds
  • A.W. and Sim, R.B., eds.),
  • 1997