C1R
C1R (complement C1r) is the serine protease subunit of the complement C1 complex and catalyses the first enzymatic step of the classical complement pathway. Once activated, it cleaves and activates C1S, the second protease of the cascade. Browse Assay Genie's current range of C1R research reagents below, or read on for the biology behind the target.
C1R is a serine protease component of the C1 complex, the multiprotein assembly that initiates the classical pathway of the complement system. This cascade leads to phagocytosis and breakdown of pathogens, and to signalling that strengthens the adaptive immune system. The C1Q subcomplex of C1 associates with IgG or IgM immunoglobulins complexed with antigens, forming antigen-antibody complexes on the surface of pathogens. This activates C1R: immunoglobulin binding promotes its autocatalytic cleavage.
Activated C1R then cleaves and activates C1S, the second protease of the classical pathway. It remains unclear whether C1R activates C1S within single, strained C1 complexes or between neighbouring C1 complexes on surfaces. The protein is annotated as secreted and found at the cell surface, and it belongs to the peptidase S1 family. HGNC places it among the serine proteases, the Sushi domain containing proteins and the complement system activation components.
The human C1R gene encodes this proteolytic subunit, which was previously named complement component 1, r subcomponent. As part of the complement system, it contributes to innate immune defence, ultimately triggering phagocytosis, inflammation and rupture of the bacterial cell wall. Mutations in the C1R gene are associated with Ehlers-Danlos syndrome. The mouse ortholog is C1rb.
C1R catalyses the first enzymatic step of the classical pathway, making it a central protease for studying how complement activation begins.
As a subunit of the C1 complex, C1R contributes to phagocytosis, inflammation and lysis of bacterial cell walls in the innate immune response.
C1R activation follows C1Q binding to immunoglobulin-antigen complexes, a link between adaptive antibody responses and complement signalling.
Mutations in the C1R gene are associated with Ehlers-Danlos syndrome, linking this complement protease to a connective tissue disorder.
C1R is the serine protease of the C1 complex. When C1Q binds antigen-complexed IgG or IgM, immunoglobulin binding promotes autocatalytic cleavage and activation of C1R. Activated C1R then cleaves and activates C1S, the second protease of the classical complement pathway.
The HGNC name is complement C1r, and UniProt lists the protein as complement C1r subcomponent. The previous HGNC name was complement component 1, r subcomponent. No alternative gene symbols are recorded. The enzyme is classified as EC 3.4.21.41.
The mouse ortholog is C1rb. C1R belongs to the peptidase S1 family. In humans, mutations in the C1R gene are associated with Ehlers-Danlos syndrome. Check the datasheet of any product for its validated reactivity.
Other C1 complex components, classical pathway proteases and complement system targets with products at Assay Genie.
Gene and protein annotations from HGNC, NCBI Gene and UniProt P00736; product specifications from Assay Genie datasheets.