Domains equatorial

Figure 6.12 (a) Schematic diagram of one subunit of GroEL. The polypeptide chain is folded info three domains. The equatorial domain (green) is the largest domain, comprising 10 a helices, and is built up from both the N-tetminal and the C-terminal regions. 

The apical domain (blue), which is a p sandwich flanked by a helices, is formed by the middle region of the polypeptide chain. The two linker regions between the equatorial and the apical domains form a small infermediate domain (purple) comprising three a helices. 

Because the axial positions have more close neighbors than the equatorial positions, there is more space available to a ligand or its bonding domain in an equatorial position than in an axial position. Thus nonbonding domains and larger bonding domains preferentially occupy the equatorial positions. Consequently... 

In a later publication, Kishimoto et al. (2004) proposed the water-filled nanotube as a model for the fibrillar N-terminal domain of the yeast prion Sup35p. The authors find that hydrated Sup35p fibrils show no 10-A equatorial reflection in the fiber diffraction pattern, but that dried fibrils... 

Shapes for lone pairs intermediate between those of Structure C, Fig. 25, and B, Fig. 24, may occur, Fig. 26. Such domain-shapes have, in effect, been used by Gillespie 57,86) to account for several features of Bartell and Hansen s 87> accurately determined structures of Pi s, CH3PF4, and (CH3)2PF3, and may be useful, also, in explaining why the axial bond in BrFs is evidently shorter than the equatorial bonds. 

Fig. 30 A—C. The Berry mechanism for electron-pair-coordination-number 5. (A) Trigonal bipyramidal coordination. Ligands bonded through shaded electron-domains are in axial positions. (B) Tetragonal pyramidal coordination. A slight distortion of structure A. (C) Trigonal bipyramidal coordination. A slight distortion of structure B. Ligands bonded through shaded electron-domains are now in equatorial positions...

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