A-Helical coiled coil

Dimerization of the Ce-zinc cluster transcription factors involves an a-helical coiled coil in the dimerization region. Coiled coils, often called leucine zippers, are also found in a large group of transcription factors that do not contain zinc. The leucine zipper is made up of two a helices in a coiled coil with every seventh residue leucine or some other large hydrophobic residue, such as isoleucine or valine. Leucine zipper transcription factors (b/zip) include factors characterized by heterodimerization, for example Fos and Jun. The a-helical DNA-binding motifs of the heterodimers recognize quite different base sequences and are continous with the a helices of the zipper. 

We described in Chapter 3 the basic features of a-helical coiled coils whose amino acid sequences are recognized by heptad repeats a to in which positions a and d frequently are hydrophobic residues (see Figures 3.2 and 3.3). 

Cohen, C., Parry, D.A.D. a-Helical coiled coils and bundles how to design an a-helical protein. 

Hydrogels Based on a-Helical Coiled-Coil Structures... 

Usually, TS /1-solenoids represent only parts of larger multidomain proteins. Other trimeric motifs found in these proteins include a-helical coiled coils, TS /1-spirals, trimeric bundles of single-stranded /1-solenoids, and irregular globular structures. Some of these domains may be needed for correct folding of the TS /1-solenoid. 

While structural prediction of globular proteins remains uncertain in the absence of extensive sequence similarity to protein (s) of known structure (Moult, 2005), predictions can be quite reliable for proteins with repetitive substructures. Examples include collagen (Fraser and MacRae, 197S), a-helical coiled coils (Cohen and Parry, 1994 Lupas, 1997), LRR proteins (Kajava, 2001 Kajava and Kobe, 2002), and /1-solenoids (Bateman et al., 1998 Kajava and Steven, 2006 Kajava et al, 2001 McDonnell et al., 2006). 

Structures of the two proteins were characterized using circular dichro-ism (Table 1) [35]. Both proteins were a-helical coiled coils. Although... 

Hadley, E. B. Geltman, S. H. An antiparallel a-helical coiled-coil model system for rapid assessment of side-chain recognition at the hydrophobic interface. J. Am. Chem. Soc. 2006,128,16444-16445. 

Dong H, Hartgerink JD. Role of hydrophobic clusters in the stability of a-helical coiled coils and their conversion to amyloid-like beta sheets. Biomacromolecules 2007 8 617-623. 

Melnik TN, Villard V, Vasiliev V, Corradin G, Kajava AV, Potekhin SA. Shift of fibril-forming ability of the designed a-helical coiled-coil peptides into the physiological pH region. Protein Eng 2003 16 1125-1130. 

Villard V, Kalyuzhniy O, Riccio O, Potekhin S, Melnik TN, Kajava AV, Ruegg C, Corradin G. Synthetic RGD-containing a-helical coiled coil peptides promote integrin-dependent cell adhesion. J Peptide Sci 2006 12 206-212. 

The a-helical coiled coil A versatile, amphiphilic model system 747... 

In the previous chapter we described a systematic study of the interactions of small model peptides with a rather specific enzyme. In our attempt to systematize the effects of fluorinated amino acids on peptide and protein interactions we have established a model system that lays the foundation for a more general approach. How do the steric effects and the degree of fluorination as well as the polarity of fluoroalkyl amino acid side chains affect the folding of proteins and the strength of peptide-protein interactions In order to answer this central question we choose a very common folding motive, the a-helical coiled coil. 

The a-helical coiled coil-based screening system already provided a wide variety of information about the interactions of fluorinated amino acids within hydrophobic and hydrophilic protein environments. Investigations on the thermal stability as well as the replicase activity have both emphasized the orthogonal properties of fluorinated aliphatic amino acid side chains. The term orthogonal in this context has been chosen by us to demonstrate that they are in fact hydrophobic... 

The most prominent component of the central shaft is the 270-residue subunit y, which associates loosely with the a3P3 head complex but more tightly with F0. About 40 residues at the N terminus and 60 at the C terminus form an a-helical coiled coil, which is visible in Fig. 18-14E199 211 and which protrudes into the central cavity of the a3P3 complex. Because it is asymmetric, the y subunit apparently acts as a rotating camshaft to physically alter the a and P subunits in a cyclic manner. Asymmetries are visible in Fig. 18-14D.211 The central part of subunit y forms a more globular structure, which bonds with the c subunits of F0.205 Exact structures are not yet clear. 

---