Apolipoproteins gene structures

Nielsen, L. B., Kahn, D., Duell, T., Weier, H. U., Taylor, S., and Young, S. G. 1998. Apolipoprotein B gene expression in a series of human apolipoprotein B transgenic mice generated with recA-assisted restriction endonuclease cleavage-modified bacterial artificial chromosomes. An intestine-specific enhancer element is located between 54 and 62 kilobases 5 to the structural gene, J. Biol. Chem., 273, 21800-21807. 

Evidently, the multiple functions of apolipoproteins are determined by their unique, modular structures encoded by families of genes. 

While lipoproteins are the products of many different genes, the major apolipoproteins share properties distinguishing them from most lipid-free and membrane-associated proteins. For example, apolipoproteins consist of a single polypeptide chain that has relatively little tertiary structure. Most apolipoproteins contain stretches of amphipathic alpha-helix, whose hydrophobic face can be turned to the lipid surface of the particle. The apolipoproteins are flexible, as is reflected in their unusually small free energy of unfolding. As these apolipoproteins expand and contract at the cell surface, different protein domains are exposed that are detectable with monoclonal antibodies. These properties reflect the role of apolipoproteins at the surface of lipoprotein particles whose size changes as they circulate. 

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