Repeating structures

Kajava, A.V., Vassart, G., Wodak, S.J. Modelling of the three-dimensional structure of proteins with the typical leucine-rich repeats. Structure 3 867-877, 1995. 

As shown in Figure 9.24, the outer membrane of Gram-negative bacteria is coated with a highly complex lipopolysaccharide, which consists of a lipid group (anchored in the outer membrane) joined to a polysaccharide made up of long chains with many different and characteristic repeating structures... 

Repeating Structural Elements Are the Secret of Myosin s Coiled Coils... 

Figure 14.10 Two represenlations of the repeating structural unit in CUSO4.5H2O showing the geometrical distribution of ligands about Cu and the connectivity of the unique H2O molecule.

Figure 1. Muscle development. A skeletal muscle fiber is formed by the fusion of many single cells (myoblasts) into a multinucleated myotube. Myotubes then develop into the muscle fiber (see text). Sarcomeres form in longitudinal structures called myofibrils. The repeating structure of the sarcomere contains interdigitating thick and thin filaments.

Figure 8. A schematic representation of the elements of the X-ray diffraction pattern from relaxed muscle. These reflections are interpreted to arise from various repeating structures in the muscle. Bragg s law, which states that...

Monomeric G-actin (43 kDa G, globular) makes up 25% of muscle protein by weight. At physiologic ionic strength and in the presence of Mg, G-actin polymerizes noncovalently to form an insoluble double helical filament called F-actin (Figure 49-3). The F-actin fiber is 6-7 nm thick and has a pitch or repeating structure every 35.5 nm. 

Fig. 11 (a) Schematic polymer structure of poly-7 OEt. Phenylene rings are omitted in order to simplify, (b) Molecular model of repeating structure of poly-7 OEt. Four chiral centres on each of two cyclobutane rings in both sides are enantiomeric to each other. 

Fig. 9. Repeating structure of azobenzene dendrimers. G1 (n=l), G2 (n=3), G3 (n=7), and G5 (n= 15). Right structure is G4 nitro-azobenzene dendrimer...

There are two broad kinds of polyion conformation the random coil and the ordered helix. In a helix there are regularly repeated structures along the coil there are none in the case of a random coil. In this book we are concerned with the latter where there are often several conformations with approximately equal free energies and, thus, conformational changes occur readily. 

Amyloid fibrils form from a variety of native proteins with diverse sequences and folds. The classic method for the structural analysis of amyloid has been X-ray fiber diffraction amyloid fibrils exhibit a characteristic diffraction signature, called the cross-/) pattern. This cross-/ pattern suggested a repeating structure in which /1-sheets run parallel to the fiber axis with their constituent /1-strands perpendicular to that direction (Sunde and Blake, 1997). This diffraction signature pointed to an underlying common core molecular structure for the amyloid fibril that could accommodate diverse sequences and folds. A number of groups have proposed amyloid folds that are consistent with the experimental data and these can be linked to repeating /1-structured units. 

The interphotoreceptor retinoid-binding protein (Borst et al., 1989) functions in the regeneration of rhodopsin in the mammalian visual cycle. It is exclusive to vertebrates yet contains a repeated structure that has been found singly in bacterial and plant tail-specific proteases (TSPc) (Silber et al., 1992) and the archaeal tricorn protease (Tamura et al., 1996). The eukaryotic homologs of TSPc are likely to be inactive as... 

DNA is packaged in the nucleus into the form of chromatin. Chromatin is a nucleoprotein complex composed of histone and non-histone proteins, DNA and RNA and it exhibits a repeating structure (van Holde, 1988). The basal unit of chromatin, the nucleosome, is composed of a histone octamer (two each of H2A, H2B, H3 and H4) around which two superhelical turns of DNA are wrapped (van Holde, 1988). The structure of both the histone octamer (Arents et al, 1991)... 

Arents G, Moudrianakis EN (1993) Topography of the histone octamer surface repeating structural motifs utilized in the docking of nucleosomal DNA. Proc Natl Acad Sci U S A 90 10489-10493... 

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