C1R Human

C1r enzyme is the activated form of C1r proenzyme which is inactive zymogen until C1 is activated.C1r is a subunit of the C1 complex which is the first complement component in the classical pathway of complement. C1 is a non-covalent calcium-dependent complex containing1 C1q, 2 C1r and 2 C1s molecules.Each C1q bindsthe Fc domains of IgG or IgM by using2 or more of its six arms. The binding of multiple arms to immune complexes causesthe production of 2 proteases that cleave and activate the 2 C1s protease zymogens in the complex by the C1r proteins. The activation of C1r results from cleavage of C1r into 2 fragments of 57,000 and 35,000 Dalton.