A group of apolipoproteins that can readily exchange among the various classes of lipoproteins (HDL; VLDL; chylomicrons). After lipolysis of triglycerides on VLDL and chylomicrons, Apo-C proteins are normally transferred to HDL. The subtypes can modulate remnant binding to receptors, LECITHIN cholesterol ACYLTRANSFERASE, or lipoprotein lipase.