C1 Complex

Background

Complement component C1 is a large inactive protein complex in the plasma, which is composed of one C1q, two C1r, and two C1s. The C1q subunit can bind to the Fc regions of two antigen-specific antibodies that have bound in close proximity to antigen fixed on the surface of a pathogen. Binding of the C1q subunit activates the C1r subunits and then C1s subunits are activated. Following, the activated C1s subunits can cleave serum C4 into C4a and C4b. Then after a series of reactions, the C3 convertase and C5 convertase formed and classical pathway is activated.

Fig.1 Diagram of complement receptors and ligands.^1,3

C1q is made up of six heterotrimers each containing the C1qA, C1qB, and C1qC chains. Each chain of C1q has a central region forming a collagen stem together with the equivalent regions of the other two chains. The structures of C1r and C1s are similar, and both of them have the domain architecture CUB1-EGF-CUB2-CCP1-CCP2-SP. Recently, several researchers have found broad C1 functions beyond the complement system. C1q binds to the Frizzled receptors to activate C1s, which cleaves lipoprotein receptor-related protein 6 to trigger aging-associated Wnt receptor signaling. Beside, C1q binds to apoptotic cells and the activated C1 proteases cleave nuclear antigens.

C1 Complex Functional Service

Creative Biolabs provides native human Complement C1 Complex Protein, which is available for functional assays. C1 Complex protein plays a crucial role in the initiation of the classical complement pathway, essential for immune response. Our C1 Complex product offers high purity and is ideal for a variety of functional assays, including complement activation and immune system research.

Fig.2 Role of C1 Complex in the classical pathway activation.^2,3

C1 Complex functional/activity tests aim to evaluate the function or activity of the C1 Complex in immune response modulation. Common methods for testing include ELISA, complement activation assays, and flow cytometry to assess binding and activation. These tests help in understanding how C1 Complex interacts with antibodies and pathogens, leading to complement cascade initiation. Research has shown that alterations in C1 Complex functionality can be linked to various immune-related disorders, such as autoimmune diseases and complement deficiencies. Through these functional tests, we assist researchers in characterizing the C1 Complex for better diagnostic and therapeutic strategies.

Creative Biolabs offers comprehensive C1 Complex-functional services, including custom assay development. By leveraging our expertise, we assist clients in designing and executing experiments, helping customers optimize their research that yields valuable insights into the role of the C1 Complex. Additionally, we provide individual components of the C1 Complex, such as C1r, C1q, and C1s, for targeted functional and activity testing services.

Click the following targets to view our C1 product lists.