Zipper complexes

Wendt, H., Durr, E., Thomas, R. M., Przybylski, M., and Bosshard, H. R. (1995). Characterization of leucine zipper complexes by electrospray ionization mass spectrometry. Protein ScL, 4, 1563-70. 

Figure 10.20 A chemical double mutant cycle to assess the strength of edge-to-face n-n interactions (thick dashed wedges) in a molecular zipper complex AAG = AGA — ACB — AGc + A )>...

A series of amide oligomers have been prepared from isophthalic acid and bisaniline derivatives. These compounds assemble into double-stranded zipper complexes in solution via hydrogen-bonding and edge-to-face aromatic interactions. The stabihty and structures of the complexes were determined by H NMR in chloroform solution. 

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. 

Activator Protein-1 (API) comprises transcriptional complexes formed by dimers of members oftheFos, Jun, and ATF family of transcription factors. These proteins contain basic leucine zipper domains that mediate DNA binding and dimerization. They regulate many aspects of cell physiology in response to environmental changes. 

An analogous type of lithium-induced zipper cyclization was observed with PAM 5, affording the mesolDL pair of helicenes (Scheme 11) [34]. PAM 5 also reacted with dicobaltoctacarbonyl to give a tetracobalt cluster in which only two of the triple bonds have been complexed [35]. 

Regarding efficiency in terms of achieving a maximum increase of molecular complexity in a minimum number of operational steps, the zipper-mode tetracyclization of the open-chain trienediyne 102 leading to the tetracyclic steroidal skeleton 103, as accomplished by Negishi et al. is particularly impressive (Scheme 28). This transformation involves four intramolecular carbopalladations with two alkyne relays forming four new G,G-bonds with the creation of four rings. 

Fig. 1.7. Basic leudne zipper and heltx-loop-heltx motif in complex with DNA. A) The basic leucine zipper of the transcription activator GCN4 of yeast consists of two slightly curved a-hehces, which dimerize with the help of the leucine zipper motif. The sequence specific binding of DNA occurs via the basic ends of the two helices. They insert themselves into the major groove of the DNA. B) The helix-loop-helix motif of the eucaryotic transcription factor Max complexed with DNA. Molscript drawing (Kraulis 1991).

Jun is actually a multigene family whose encoded proteins bind to DNA as complexes formed with the 62 kDa phosphoprotein Fos, the product of the c-fos gene.460 The heterodimeric Fos/Jun complex is held together, at least in part, by interactions between leucine side chains lying along a pair of parallel a-helices in a "leucine zipper" (Fig. 5-36 Fig. 2-21).461 462... 

Each of the monomeric proteins c-jun and c-fos, as well as other members of the leucine zipper family, has an N-terminal DNA-binding domain rich in positively charged basic amino acid side chains, an activation domain that can interact with other proteins in the initiation complex, and the leucine-rich dimerization domain.363 The parallel coiled-coil structure (Fig. 2-21) allows for formation of either homodimers or heterodimers. However, cFos alone does not bind to DNA significantly and the cjun/cFos heterodimer binds much more tightly than does cjun alone.364 The yeast transcriptional activator protein GCN4 binds to the same 5 -TGACTCA sequence as does the mammalian AP-1 and also has a leucine zipper structure.360 364 365... 

Furthermore, this complexation/dissociation change may occur with an accompanying cooperative chain-chain zipper effect the drastic change or transition of solubility implies extensive chain-chain interactions. 

Fig. 12. Zipper effect in the process of formation and dissociation of interpolymer complex...

The most striking difference between DNA-binding proteins in prokaryotes and eukaryotes has to do with the symmetry of the interaction. In prokaryotes the binding proteins almost always interact in a symmetrical fashion with the DNA. In eukaryotes most of the cases that have been examined so far involve proteins that interact in an asymmetrical fashion with the DNA. In many cases the regulatory proteins interact in multisubunit complexes that contain nonidentical subunits. Four different types of structural motifs are discussed The homeodomain, the zinc finger, the leucine zipper, and the helix-loop-helix. 

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