Acts upstream of or within defense response to bacterium and immune response. Predicted to be located in extracellular region. Predicted to be part of membrane attack complex. Predicted to be active in extracellular space. Is expressed in epidermis; gut; liver; periderm; and pharyngeal arch 3-7 skeleton. Human ortholog(s) of this gene implicated in complement component 6 deficiency. Orthologous to human C6 (complement C6).