Basic region

The GCN4 basic region leucine zipper binds DNA as a dimer of two uninterrupted a helices... 

Figure 10.22 Sequence-specific interactions between one of the a-helical basic regions of GCN4 (blue) and bases in the DNA fragment (red). The methyl groups of the thymine bases are shown as spheres.

Figure 10.23 Domain arrangement along the polypeptide chains of three families of transcription factors b/z, b/HLH and b/HLH/z. All three have a basic region (blue) that binds DNA. Dimerization is achieved by the zipper region (purple) in the b/z family, by the Hl-loop-H2 region (red-yellow-green) in the b/HLH family and by a combination of both the zipper and the HLH regions in the b/HLH/z family.

Figure 10.24 Structure of a monomer of the DNA-binding domain of the transcription factor MyoD. The domain, which belongs to the b/HLH family, comprises two a helices joined by a loop region. The basic region (blue) and the first helix HI (red) of the helix-loop-helLx region form one continous a helix. (Adapted from P.C.M. Ma et al.. Cell 77 451-459, 1994.)...

The a-helical basic region of the b/HLH motif binds in the major groove of DNA... 

Figure 10.28 Schematic diagram of the binding of the transcription factor Max to DNA. The two monomers of Max (blue and green) form a dimer through both the helix-loop-helLx regions which form a four-helix bundle like MyoD, and the zipper regions, which are arranged in a coiled coil. The N-terminal basic regions bind to DNA in a way similar to GCN4 and MyoD. (Adapted from A.R. Ferre-D Amare et al., Nature 363 38-4S, 1993.)...

The helical basic region of Max binds to the major groove of DNA in the same manner as MyoD (see Figures 10.26 and 10.28). The DNA structure is essentially that of B-DNA with minor distortions as in the MyoD complex. Both Max and MyoD recognize the same consensus half-site DNA sequence 5 -CAC-3 ... 

Ellenberger, T.E., et al. The GCN4 basic region leucine zipper binds DNA as a dimer of uninterrupted a helices crystal structure of the protein-DNA complex. Cell 71 1223-1237, 1992. 

Cholanic acid also possesses the ability of transporting cations across a lipophilic membrane but the selectivity is not observed because it contains no recognition sites for specific cations. In the basic region, monensin forms a lipophilic complex with Na+, which is the counter ion of the carboxylate, by taking a pseudo-cyclic structure based on the effective coordination of the polyether moiety. The lipophilic complex taken up in the liquid membrane is transferred to the active region by diffusion. In the acidic region, the sodium cation is released by the neutralization reaction. The cycle is completed by the reverse transport of the free carboxylic ionophore. 

Carboxylic ionophores selectively transport cations by using intramolecular complexation in the uptake process of cations (basic region). A new ion transport system has been developed which incorporates a structural device which assists in the release process by using intramolecular complexation of an [18]crown-6 ring and a primary ammonium ion 48>. The experimental conditions are shown in Fig. 7. All these com-... 

Some purely major groove-binding TFs, such as the basic-region leucine zipper (bZIP) protein GCN4, can co-occupy the DNA helix in the presence of polyamides [72]. Modified polyamides with an attached Arg-Pro-Arg tripeptide can interfere with major groove-binding proteins by disrupting key phosphate contacts, distort-... 

Here BK stands for "Bom-von K man" and denotes the basic region of periodicity... 

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