Lipoproteins structural organization

A30. Atkinson, D., Tall, A. R., Small, D. M., and Mahley, R. W., The structural organization of the lipoprotein HDLj. from atherosclerotic swine. Structural features relating the particle surface and core. Biochemistry 17, 3930-3933 (1978). 

The general structural organization is similar for all the lipoprotein classes the apolipoproteins and amphipathic lipids (mostly phospholipids (PL) and unesterified cholesterol) form a 20-A-thick shell on the surface of spherical particles. This shell encloses the core of neutral lipids (triacylglycerols, cholesteryl esters (CE), and small amounts of unesterified cholesterol and other dissolved lipids, e.g., lipid-soluble vitamins). The main protein components are characteristic of each lipoprotein class they are indicated in Fig. 1, and will be described in detail in Section 3 of this chapter. 

Davidson, W.S., Silva, R.A.G.D. 2005. Apolipoprotein structural organization in high-density lipoproteins belts, bundles, hinges and hairpins. Curr. Opin. Lipidol. 16 295-300. 

Sterols and structurally similar molecules are present in almost all forms of marine life (Morris and Culkin, 1977). Their role as hormonal regulators of growth and reproduction and their incorporation in lipoprotein structures has been briefly discussed in a previous chapter (Gagosian and Lee, Chapter 5). Considerable interest has recently been shown in the determination of trace amounts of these biologically active substances. Due to the high diversity of their molecular structures, the steroid compounds lend themselves to use as tracers of processes involving labile organic matter. 

Sorci-Thomas, M. G., Owen, J. S., Pulp, B., Bhat, S., Zhu, X., Parks, J. S., Shah, D. et al. 2012. Nascent high density lipoproteins formed hy ABCAl resemble lipid rafts and are structurally organized by three ApoA-I monomers,./ TJnid Res 53, 1890-1909. 

Structure of human plasma low-density lipoproteins molecular organization of the central core, Proc. Nat. Acad. Sci. U.S.A., 74 1042. 

In addition to small organic molecules or metal ions, proteins may have other components tightly associated with them. Nucleoproteins, for instance, contain noncovalently bound DNA or RNA, as in some of the structural proteins of viruses. Lipoproteins contain associated lipids or fatty acids and may also carry cholesterol, as in the high-density and low-density lipoproteins in serum. 

Antigens usually are macromolecules that contain distinct antigenic sites or epitopes , which can be recognized and interact with the various components of the immune system. They can exist as individual molecules composed of synthetic organic chemicals, proteins, lipoproteins, glycoproteins, RNA, DNA, polysaccharides—or they may be parts of cellular structures (bacteria or fungi) or viruses (Male et al., 1987 Harlow and Lane, 1988). 

ApolipoprcHein C ll serves as a ccifactor for lipoprotein lipase. This situation resernbSes that of colipase, which is required for the activity of pancieatic lipase. When chylomicrons or VLDLs pass through the capillaries of an organ, they encounter lipoprotein lipase. About half the fatty acids liberated by the action of this enzyme are taken up by the tissue, whereas the rest remain in the circulation and return bound to albumin) to the liver. Apo C-II is part of the structure of chylomicrons and VLDI,. ... 

The elucidation of the structure of any lipoprotein, i.e., the organization of the protein and lipid components, is a challenging problem, because it relies on several techniques that give only partial and approximate information. Structural models should be consistent with experimental data that characterize the physiological role and the physicochemical properties of the lipoprotein and its components. Considerable effort has been expended to fit experimental data to structural models of mammalian lipoproteins (Zilversmit, 1965 Sata et al., 1972 Schneider et al., 1973 Havel, 1975 Verdery and Nichols, 1975 Shen et al., 1977 ... 

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