Evolving functions of apolipoprotein AIV: from birds to mammals

Apolipoprotein (apo) AIV is a serum protein that displays particularly vivid dynamics regarding its distribution among the various plasma lipoprotein and nonlipoprotein fractions. This article discusses two main aspects. First, the general functional properties of apo AIV as a highly mobile and versatile apolipoprotein, delineated in mammalian species, are described. Second, the implications of the fact that not only mammals, but also the chicken, express apo AIV are highlighted. Given the differences in certain lipid metabolic pathways between mammals and birds, the structure and functions of apo AIV may have evolved into distinct functions in different amniotes.