Low-density lipoproteins structure

Cholesteric liquid-crystals and low-density lipoprotein structures... 

APOLiPOPROTEIN B AND LOW-DENSITY LIPOPROTEIN STRUCTURE IMPLICATIONS FOR BIOSYNTHESIS OF TRIGLYCERIDE-RICH LIPOPROTEINS... 

The Sema domain consisting of about 500 amino acids is characterized by highly conserved cysteine residues that form intramolecular disulfide bonds. Crystal structures have revealed that the Sema domain folds in the manner of the (3 propeller topology which is also found in integrins or the low-density lipoprotein (LDL) receptors. Sema domains are found in semaphorins, plexins and in the receptor tyrosine kinases Met and Ron. 

Esterbauer, H., Dieber-Rotheneder, M., Waeg, G., StreigI, G. and Jurgens, G. (1990). Biochemical structural and functional properties of oxidised low density lipoprotein. Chem. Res. Tox. 3, 77-92. 

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. 

An impressive example for the successful use of domino reactions for the synthesis of pharmacological lead structures was described by Paulsen et al1241 Recently, the difluoro compound 57 has been identified as highly potent inhibitor of the cholesterin-ester-transferprotein (CETP), which is responsible for a transfer of cholesterin from high-density lipoprotein (HDL) to low-density lipoprotein (LDL). This clearly results in an increase of LDL and a decrease of HDL which raise the risk of coronary heart desea-ses. The core structure of 57 is now accessible efficiently by a combination of a Mukaiyama-MichaeL... 

In the majority of cases, fluorescent labels and probes, when studied in different liquid solvents, display single-exponential fluorescence decay kinetics. However, when they are bound to proteins, their emission exhibits more complicated, nonexponential character. Thus, two decay components were observed for the complex of 8-anilinonaphthalene-l-sulfonate (1,8-ANS) with phosphorylase(49) as well as for 5-diethylamino-l-naphthalenesulfonic acid (DNS)-labeled dehydrogenases.(50) Three decay components were determined for complexes of 1,8-ANS with low-density lipoproteins.1 51 1 On the basis of only the data on the kinetics of the fluorescence decay, the origin of these multiple decay components (whether they are associated with structural heterogeneity in the ground state or arise due to dynamic processes in the excited state) is difficult to ascertain. 

In this section several recently published studies on the interaction of nonionic surfactants with a variety of biological systems, including enzymes, bacteria, erythrocytes, leukocytes, membrane proteins, low density lipoproteins and membranes controlling absorption from the gastrointestinal tract, nasal and rectal cavities, will be assessed. This is a selective account, work having been reviewed that throws light on structure-activity relationships and on mechanisms of surfactant action. 

Steroids that aid in muscle development are called anabolic steroids. They are synthetic derivatives of testosterone, thus have the same muscle-building effect as testosterone. There are more than 100 different anabolic steroids which, vary in structure, duration of action, relative effects and toxicities. Androstenedione, stanozolol and dianabol are anabolic steroids. They are used to treat people suffering from traumas accompanied by muscle deterioration. The use of anabolic steroid can lead to a number of dangerous side-effects, including lowered levels of high density lipoprotein cholesterol, which benefits the heart, and elevated levels of harmful low density lipoprotein, stimulation of prostate tumours, clotting disorders and liver problems. 

Fig. 5.2.6 Long-distance polymerase chain reaction (PCR) to detect large deletions and insertions in the low-density lipoprotein receptor (LDLR). The structure of the LDLR gene is shown from exon 1 through 18. The five fragments produced by the five long-distance PCRs are outlined. PCR1 covers exons 1-5, PCR2 exons 6-13, PCR3 exons 15-18, PCR 4 exons 2-10, and PCR5 exons 12-18...

FIGURE 21-39 Lipoproteins. (a) Structure of a low-density lipoprotein (LDL). Apolipoprotein B-100 (apoB-100) is one of the largest single polypeptide chains known, with 4,636 amino acid residues (M, 513,000). (b) Four classes of lipoproteins, visualized in the electron... 

Some proteins are imported into cells from the surrounding medium examples in eukaryotes include low-density lipoprotein (LDL), the iron-carrying protein transferrin, peptide hormones, and circulating proteins destined for degradation. The proteins bind to receptors in invaginations of the membrane called coated pits, which concentrate endocytic receptors in preference to other cell-surface proteins. The pits are coated on their cytosolic side with a lattice of the protein clathrin, which forms closed polyhedral structures (Fig. 27-40). The clathrin lattice grows as more recep-... 

Davis, R., Lipoprotein structure and secretion. In D. E. Vance, and J. E. Vance (eds.), Biochemistry of Lipids, Lipoproteins and Membranes. Amsterdam Elsevier Science Publishers, 1991. This chapter (14) provides an advanced discussion on the assembly and secretion of very-low-density lipoproteins. 

---