Tetrameric assembly

Both AMPA and NMDA receptors are multimeric, probably tetrameric, assemblies of various molecularly distinct subunits, giving rise to large receptor diversity. For AMPA receptors this is achieved by assembling the... 

A tennis-ball-shaped molecular aggregate can be constructed by the self-assembly of curved molecule I. Tetrameric assembly of II generates a pseudo-spherical capsule. Dimeric assembly of III can be induced by the encapsulation of smaller molecules of appropriate size and shape at the center of a spherical complex. 

Gel filtration of purified 6-MSAS indicates that it is a 750 kDa homotetramer [120]. When treated with 1,3-dibromopropanone (DBP), 6-MSAS behaves similarly to animal FASs and inactivation occurs concomitantly with its cross-linking to a covalent homodimer. By analogy to the well-characterized DBP cross-linked yeast and animal FASs [61,62,79,80], DBP is suggested to cross-link active site sulfhydryl residues of the -ketoacyl synthase cysteine and the AGP pantetheine. This notion is supported by the observation that preincubation with either acetyl or malonyl CoA precludes cross-linking. Thus, the functional significance of the tetrameric assembly of 6-MSAS remains a mystery. 

Reaction of the uranyl cation with the divacant lacunary anion y-[SiWio036] (Figure 5b) yields two species in approximately equal proportions according to Si- and W-NMR spectra. Crystals of one of these complexes have been structurally characterized as the tetrameric assembly [(M(H20))4(U02)4( i-OH)2(SiWio036)4] (M = Na, K ) shown in Figure 11. [53]... 

Bourne Y, Taylor P, Bougis PE et al. (1999). Crystal structure of mouse acetylcholinesterase. A peripheral site-occluding loop in a tetrameric assembly. J Biol Chem, 274, 2963-2970. 

Colloc h, N. Girard, E., Dhaussy, A.-C., Kahn, R., Ascone, I., Mezouar, M., Fourme, R. High-pressure macromolecular crystallography The 140-MPa crystal structure at 2.3 A resolution of urate oxidase, a 135-kDa tetrameric assembly, Biochim Biophys. Acta. 1764 (2006) 391—397. 

Scheme 4-3 Synthesis of cyclic trimeric and tetrameric assemblies from A,C bisbenzyl ether 4. The four OH-groups in the cavitand are labelled A, B, C, D.

F ore 5 Representation of the tetrameric assembly of dimeric molybdenum(V) centres in... 

Fig. 14 Dynamic equilibrium between the trimeric and tetrameric assemblies, 28 and 29...

Another p-modified derivative, p-benzo-fused 17b, which possesses an extended TT-structure, provided a mesophase with TATA Cl as a tetragonal columnar (Coltet) phase with a = 4.21 nm and c = 0.73 nm based on a tetrameric assembly (Z = 4.02 forp = 1) (Fig. 4.12a). The mesophase range of 17bCl -(TATA ) was 24-102 °C. On the other hand, anion-free 17b formed a mesophase (33-166 °C) based on a Coin phase (a = 4.15 nm and c = 0.42 nm) consisting of a self-assembled dimer unit. In contrast to the assembled mode of the Colh structure of 14c C1 -(TATA - ), the receptor unit in 17b Cl -(TATA )+ faces the center of the circular unit with anions arranged on the inside, presumably because of the positions of the alkyl chains at the fused-benzo units at the p-positions of the pyrrole [31e]. 

The three K-channels listed above are tetrameric assemblies with subunits sharing the same signature amino acid sequence TXGYGD of the selectivity filter. Also common is the topology of the ionic permeation channel, composed of two transmembrane helices (inner and outer helix) per subunit. The two transmembrane helices are joined by a pore sequence constructed with a shorter pore helix plus the selectivity filter segment. 

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