Isoform heterogeneity and lipid affinity of human lymph and plasma apolipoprotein A-IV

We have compared the physical properties and lipid affinity of apolipoprotein A-IV isolated from lymph chylomicrons and from lipoprotein-depleted plasma. Lymph and plasma apolipoprotein A-IV demonstrated distinctly different charge properties as assessed by anion exchange chromatography and isoelectric focusing. These differences were not attributable to disparities of amino acid or sialic acid content. Lymph apolipoprotein A-IV displayed a significantly higher affinity than plasma apolipoprotein A-IV for particles of a phospholipid-triglyceride emulsion. We conclude that the charge properties of human lymph and plasma apolipoprotein A-IV may determine conformational states which alter its ability to bind to the surface of lipid particles.