Enables complement binding activity. Involved in several processes, including negative regulation of activation of membrane attack complex; negative regulation of complement-dependent cytotoxicity; and positive regulation of T cell proliferation. Located in compact myelin; extracellular space; and sarcolemma. Used to study anterior uveitis; colorectal carcinoma; glomerulonephritis; nephrosis; and neuromyelitis optica. Biomarker of acute necrotizing pancreatitis; diabetic retinopathy; and myocardial infarction. Human ortholog(s) of this gene implicated in colorectal carcinoma and ovarian cancer. Orthologous to human CD59 (CD59 molecule (CD59 blood group)). [provided by Alliance of Genome Resources, Apr 2022]