Major acute phase protein. Homohexamer; dimer of trimers. Can form amyloid fibrils after partial proteolysis; the native, undenatured protein does not form amyloid fibrils (in vitro). Apolipoprotein of the HDL complex. Binds to heparin (By similarity). Detected in blood plasma (at protein level). Detected in liver. By bacterial lipopolysaccharide. Belongs to the SAA family.