Turn protein

Individual membrane lipids and proteins turn over independently and at different rates. 

F.A. Etzkorn, J.M. Travins, S.A. Hart, Rare protein turns y-turn, helix-turn-helix, and cis-proline mimics, Adv. Amino Acid Mimet. Peptidomimet. 2 (1999) 125-163. 

To form a globular protein, a polypeptide chain must repeatedly fold back on itself. The turns or bends by which this is accomplished can be regarded as a third major secondary structural element in proteins. Turns often have precise structures, a few of which are illustrated in Fig. 2-24. As components of the loops of polypeptide chains in active sites, turns have a special importance for the functioning of enzymes and other proteins. In addition, tight turns are often sites for modification of proteins after their initial synthesis (Section F). 

Historically, coiled coils were identified with long fibrous molecules, from which their structural properties had been determined. Fiber diffraction studies on proteins of the k-m-e-f class were highly successful, initially on dried specimens but later also on native samples (Cohen and Holmes, 1963). However, these proteins turned out to be very difficult to analyze by high-resolution X-ray crystallography for the same reasons that made them so amenable to fiber diffraction—their tendency to aggregate into fibers rather than crystals and the extreme dimensions of their asymmetric units. It took decades to obtain a working structure for tropomyosin [at 15 A resolution (Phillips et al., 1986) at 9 A (Whitby et al.,... 

The synthesis of conformationally constrained bicyclic and tricyclic compounds, obtained via 5-Exo-Trig iodocyclisation of polybenzylated sugars with an allylic substituent at the anomeric position, is described. The conformation of these molecules has been studied by n.O.e. experiments and Molecular Dynamics calculations. The introduction of an amino and a carboxylic group resulted in the formation of conformationally constrained bicyclic glyco-aminoacids that mimic protein turn conformation. 

R and 37-S are characterized by very similar, even if not identical, structural properties of the two 5-member rings. The distance between the C=0 and the NH2 groups is about 7 A for 37-R and 8 A for 37-S. Moreover, the orientation of the NH2 group in 37-R seems more suited to mimic protein turn mimetics. 

One of the reasons that different tissues/organs contribute differently to SMR is because they are specialized for different kinds of energydemanding functions. As a rough approximation for mammals, the dominant ATP sinks or ATP-consuming processes are protein turn-... 

The performance of protein or antibody microarrays is dependent on various factors. One of these is the use of an appropriate microarray surface for the immobilization of the protein or antibody samples. Most conventional microarray surfaces have been adapted from DNA chip technology. DNA can easily be immobilized by electrostatic interactions of the phosphate backbone onto a positively charged surface. In contrast to DNA, as already mentioned, proteins are chemically and structurally much more complex and show variable charges, which may influence the efficiency of protein attachment. Additionally, proteins lose their structure and biochemical activity easily. For example, globular proteins consist of a hydrophilic exterior and a hydrophobic interior. When immobilized on a hydrophobic surface, the inside of the protein turns out, which may destabilize the structure and, simultaneously, the activity of the protein. These considerations demonstrate the complex requirements for protein immobilization. 

Planz, G., K. Quiring, and D. Palm. Rates of Recovery of Irreversibly Inhibited Monoamine Oxidases A Measure of Enzyme Protein Turn-over. Naunyn-Schmiedeburg s Arch. Pharmacol. 2J (1972) 27-42. 

Goody RS. signal transduction How G proteins turn off Nature372 220-221,1994. 

In drug-induced liver damage, a similar immunological mechanism is conceivable the respective medicament acts as a hapten, and an endogenic protein turns into an autoantigen. In hypersensitivity reactions, IgE can increase. 

When proteins precipitate with heating, it is because the protein turns inside-out, exposing many of the lipophilic amino add residues (residues previously facing the inner core of the protein) to the external aqueous environment. The process of turning inside-out is called denaturation. The lipophilic amino acids... 

In the previous section we computed thermal transport coefficients for a water cluster whose size is reasonably similar to that of a typical globular protein. The calculation of thermal transport properties of proteins turns out not to be so simple. For one thing, there is considerable computational and experimental evidence to suggest that energy transport in proteins is non-Brownian. 

Gadsby, D.C., Vergani, P., and Csanady, L. (2006) The ABC protein turned chloride channel whose failure causes cystic fibrosis. Nature, 440, 477-483. 

In the case of interactions between inclusions in lipid bilayers (Figure 5.19) the elasticity of the bilayer interior must also be taken into account. The calculated energy of capillary interaction between integral membrane proteins turns out to be of the order of several Hence, this interaction can be a possible explanation of the observed aggregation of membrane proteins. The lateral capillary forces have been calculated also for the case of particles captured in a spherical (rather than planar) thin liquid film or vesicle. ... 

For proteins, structure corresponds to activity. If thiols influence the structure of proteins, then they also affect their activity. In other words, the oxidation state of thiols can act as a molecular switch for thiol-containing proteins, turning their activity on and off. The list of proteins with sensitive thiol groups is growing all the time, and is now known to include some of the most important transcription factors (proteins that bind to DNA and stimulate the transcription of genes to produce new proteins). Whether these factors bind to DNA or not, even whether they journey into the nucleus at all, depends on the status of their thiol groups. 

Why don t proteins turn around in biological membranes like revolving doors ... 

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