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RESEARCH PRODUCT

C1q

subject

description

Publisher Summary This chapter provides information to the physical properties, structure, and function of C1q protein. This protein is made up of three individual polypeptide chains, A, B and C, which are synthesized as pre-molecules with 22, 25, and 28 amino acid leader sequences, respectively. C1q has a characteristic appearance under the electron microscope, with six globular heads connected by six collagen-like stalks forming a central fibril stem. Glucosylgalactosyl disaccharide units are linked to certain hydroxylysine residues in the collagen regions of all three chains. C1q has a critical function in host defense and clearance of immune complexes. Antibody-independent activation of the classical pathway via C1q is evaluated for certain viruses, gram-negative bacteria, DNA, and polyanions. Activation of C1 initiates the activation of classical pathway of complement. After activation, the C1 complex is dissociated by the C1 esterase inhibitor (C1-INH). C1q-bound immune complexes bind to C1q receptors on various cell types.