Transconformation

Denaturation of myosin and actomyosin has so far been ascribed to intermolecular aggregation, but recent investigations have shown that intramolecular transconformation, the unfolding of the polypeptide chains, occurs in globular proteins and in subunits with globular structures. 

Ribonuclease Analysis of low-temperature, low pH transconformations from Tyr A-spectra Hermans and Scheraga (1961a, b)... 

Acid A-speotrum of lysozyme is sensitive to ionic strength, does not involve transconformation Intensive studies on thermal- and acid-generated transconforma-tions... 

In systems described in Sections XIV-XVI, the 1,4-arrangement of heteroatoms is not expected to affect the relative importance of the transconformation shown by indolizidine. In line with this, the perhydro-pyrrolo[2,l-c][l,4]oxazin-3-one has been shown to adopt the trans-conformation (505) (74CC395) (see Section XV). 

It has been shown in this laboratory that the equilibrium between the dimer and monomer forms of /3-lactoglobulin can be shifted by lowering the temperature It is known that /3-Iactoglobulin can be dissociated into subunits a and /3 between pH 6.0 and 9.0 in aqueous solutions at room temperature. The dimeric form ( ,/3) is stable between pH 3.0 and 6.0. Above pH 9.0 the dissociation into a and /3 subunits is irreversible owing to a transconformation termed R — S, leading to agregation (nS —> Sn). These processes can be schematized as follows ... 

According to different conformational studles(, ), these compounds are present "only" as the conformer In which the methyl group Is els to the electronpalr and trans to the N-substltuent. In such a conformer both sides of the ring are shielded by a substituent and It may be assumed that this causes a lowering of the nucleophilic reactivity. Now the question arises whether the (observed) low reactivity Is due to the presence of only one (less reactive) transconformer or Is the consequence of an equilibrium between a predominant non-reactlve trans-conformer and the reactive cls-conformer. 

PPIases are also associated with motor proteins the first PPIase domain of hFKBP52 (and to a lesser extent hCyp40) binds to the microtubule-associated motor protein dynein [21] and some authors propose that the amino acyl proline CTI plays an important part in the protein transconformation that directs relative molecular motion in contractile muscle fibers [22]. However, there is presently no evidence that PPIases are directly implicated in muscle diseases. 

M. Carlquist, The three-dimensional structures of antagonistic and agonistic forms of the glucocorticoid receptor ligand-binding domain RU-486 induces a transconformation... 

It is the authors opinion that such an increase of the dipole moment can be associated with a change of acrylate alcohol radical conformation that takes place on substitution of the hydrogen atoms by fluorine assuming formation of the preferred (polar) transconformation of the ester group [56]. 

They could only observe the fast class at pD values around 2 and this class consists of completely exposed peptide hydrogens. The medium and slow classes appear to exchange by a mechanism in which the rate is determined by transconformational exposure of unexposed peptide groups. The rate constants for exchange of the medium or slow classes are essentially the same for trypsin and the two derivatives. The numbers of hydrogens per class are essentially the same for the medium, slow, or core classes for all three substances. These results imply that the medium, slow, or core peptide hydrogens are essentially structurally identical. 

ABSTRACT The principle of electrical spectrography and its measurement system is discussed. The phenomenon of noise in electrolytes and interfaces receives attention. Noise spectrography is found to have applications in some biomolecular systems, viz., DNA helix-to-coil transition, thermal transconformation, and salt-free premelting effects. Noise conductivity emission spectra of collagen solutions gave information on permanent dipole fluctuations and hydrodynamic properties of the system. 

Ionic Atmosphere around DNA and Direct Visualization of the Thermal Transconformation (Helix- Coil Transition)... 

The thermal transconformation or helix- coil transition is followed by an ejection of Na counterions... 

FIGURE 9. Variation of noise resistance Rn of a DNA solution in NaCl 4 x 10 mol/liter, versus the frequency v. , native DNA (chicken erythrocyte at the concentration C = 1 g/liter at 25°C) , the same native DNA at 40°C A, the same DNA after thermal transconformation (sample heated at 80°C) measured at 40°C. 

On the other hand, the increase in noise conductivity with T for temperatures above the T indicates that the number of free ions in solution increases also this phenomenon corresponds to the ejection of a percentage a. of the compensating Na counterions from the phosphate sites, during the thermal transconformation. 

Figure 11 shows the variation of N in two DNA solutions versus the temperature. Before and after the melting point T , we observe two horizontal plateaus before and after the thermal transconformation, N is constant. 

The percentage Axj/ of Na ejected during the thermal transconformation is thus given by... 

A study of the thermal transconformation of DNA has allowed us to follow the evolution of the charge parameter and the length b as functions of the temperature. 

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