Helix propagation in trifluoroethanol solutions

Storrs, Richard W.; Truckses, Dagmar M.; Wemmer, David E.

doi:10.1002/bip.360321211

Cited by 111 publications

(87 citation statements)

References 17 publications

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“…This behavior correlates well with the helix stop signal characterized in · this segment of the molecule (Rico, et al, 1983;Kim & Baldwin, 1984). It has recently been shown that the helix can be pushed through this stop signal by the presence of high TFE concentrations in the solvent (Storrs, et al, 1992). In the Apa-M5 hybrid, the helix seems to propagate further into the sequence, perhaps not terminating until the last residue.…”

supporting

confidence: 65%

“…compensated by the enthalpy of hydrogen bonds between water and the backbone amide proton or carbonyl groups in the random coiL This .competition by solvent hydrogen bonds is demonstrated by the formation of helices by short peptides in solvents containing trifl.uoroethanol (TFE). This solvent with a lower dielectric constant reduces the enthalpy ofTFE-backbone amide proton hydrogen bonds (Presta & Rose, 1988;Storrs, et al, 1992;Sonilichsen, et al, 1992), although the stabilizing effects ofTFE are entropic as well (Conio, et al, 1970). The unfavorable loss in entropy upon folding further contributes to the destabilization of short a-helices.…”

Section: The A-helixmentioning

confidence: 99%

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Structures and related properties of helical, disulfide-stabilized peptides

Pagel

1993

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supporting

confidence: 65%

Section: The A-helixmentioning

confidence: 99%

Structures and related properties of helical, disulfide-stabilized peptides

Pagel

1993

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“…However, earlier studies on the role of electrostatic interactions in the stability of the S-peptide from RNase A have shown that magnitude of the charged group effects is unaltered in the presence of TFE (Nelson & Kallenbach, 1986. A general mechanism by which TFE and other aliphatic alcohols could stabilize helices has been suggested (Conio et al, 1970;Storrs et al, 1992;Cammers-Goodwin et al, 1996). These authors suggest that TFE raises the free energy of the random coil state, because TFE-water mixtures are less able to solvate the amide group of the peptide backbone.…”

Section: Discussionmentioning

confidence: 99%

Trifluoroethanol effects on helix propensity and electrostatic interactions in the helical peptide from ribonuclease T₁

1998

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Trifluoroethanol (TFE) is often used to increase the helicity of peptides to make them usable as models of helices in proteins. We have measured helix propensities for all 20 amino acids in water and two concentrations of trifluoroethanol, 15 and 40% (v/v) using, as a model system, a peptide derived from the sequence of the a-helix of ribonuclease T I . There are three main conclusions from our studies. (1) TFE alters electrostatic interactions in the ribonuclease T I helical peptide such that the dependence of the helical content on pH is lost in 40% TFE. (2) Helix propensities measured in 15% TFE correlate well with propensities measured in water, however, the correlation with propensities measured in 40% TFE is significantly worse. (3) Propensities measured in alanine-based peptides and the ribonuclease T I peptide in TFE show very poor agreement, revealing that TFE greatly increases the effect of sequence context. Keywords: a-helix; helical propensity; peptide; ribonuclease TI ; TFE; trifluoroethanol The tendency of some short peptides to form helical structure in solution has led to their use as models for protein folding and stability. These include synthetic peptides of de novo design (some recent reviews: Chakrabartty & Baldwin, 1995; Scholtz & Baldwin, 1995;Kallenbach et al., 1996), and protein fragments (e.g., Goodman & Kim, 1989;Waltho et al., 1993;Myers et al., 1996). Structured peptides can serve as models for investigating the contribution of local interactions to protein folding and stability (Muiioz & Serrano, 1996;Myers et al., 1996).2,2,2-TrifluoroethanoI (TFE) is a co-solvent that has been shown to stabilize helical structure in peptides (Goodman et al., 1963;Nelson & Kallenbach, 1986;Jasanoff & Fersht, 1994; CammersGoodwin et al., 1996; Luo & Baldwin, 1997 and references therein). Peptide fragments of protein helices often show little helix formation in water, and TFE is frequently used to induce helix formation (Sonnischen et al., 1992;Hamada et al., 1995;Kemmink & Creighton, 1995;Yang et al., 1995;Bolin et al., 1996). Although its use is widespread, the mechanism of TFE stabilization of secondary structure is not clear. One important question is whether helix propensities of the amino acids measured in water still apply in aqueous TFE solutions. This question has been addressed recently in alanine-based peptides by Baldwin and co-workers (Rohl et al., 1996;Luo & Baldwin, 1997). For reasons that are not completely clear, in water the helix propensities are twice as large in alaninebased peptides than in peptides based on natural protein sequences. Because TFE is used so widely, it is important to compare its effect on helix formation in natural peptide sequences.Recently, we have developed a variant of the small protein ribonuclease TI (RNase T I ) and a peptide corresponding to the single a-helix of RNase T I as a model system. We have used the T I peptide/protein system previously to compare directly helix propensities in peptides and proteins (Myers et al., 1997a(Myers et al., , 1...

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“…TFE is an extensively employed structure-stabilizing solvent (35,36). Upon TFE addition, a dramatic change in the CD spectra was observed, pointing at the induction of an ␣-helical conformation (supplemental Fig.…”

Section: Crt C-t Secondary Structure Ismentioning

confidence: 98%

The Structure of Calreticulin C-terminal Domain Is Modulated by Physiological Variations of Calcium Concentration

Giraldo

Medus

Lebrero

et al. 2010

Journal of Biological Chemistry

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Calreticulin is an abundant endoplasmic reticulum resident protein that fulfills at least two basic functions. Firstly, due to its ability to bind monoglucosylated high mannose oligosaccharides, calreticulin is a central component of the folding quality control system of glycoproteins. On the other hand, thanks to its capacity to bind high amounts of calcium, calreticulin is one of the main calcium buffers in the endoplasmic reticulum. This last activity resides on a highly negatively charged domain located at the C terminus. Interestingly, this domain has been proposed to regulate the intracellular localization of calreticulin. Structural information for this domain is currently scarce. Here we address this issue by employing a combination of biophysical techniques and molecular dynamics simulation. We found that calreticulin C-terminal domain at low calcium concentration displays a disordered structure, whereas calcium addition induces a more rigid and compact conformation. Remarkably, this change develops when calcium concentration varies within a range similar to that taking place in the endoplasmic reticulum upon physiological fluctuations. In addition, a much higher calcium concentration is necessary to attain similar responses in a peptide displaying a randomized sequence of calreticulin C-terminal domain, illustrating the sequence specificity of this effect. Molecular dynamics simulation reveals that this ordering effect is a consequence of the ability of calcium to bring into close proximity residues that lie apart in the primary structure. These results place calreticulin in a new setting in which the protein behaves not only as a calcium-binding protein but as a finely tuned calcium sensor.

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Helix propagation in trifluoroethanol solutions

Cited by 111 publications

References 17 publications

Structures and related properties of helical, disulfide-stabilized peptides

Structures and related properties of helical, disulfide-stabilized peptides

Trifluoroethanol effects on helix propensity and electrostatic interactions in the helical peptide from ribonuclease T₁

The Structure of Calreticulin C-terminal Domain Is Modulated by Physiological Variations of Calcium Concentration

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Helix propagation in trifluoroethanol solutions

Cited by 111 publications

References 17 publications

Structures and related properties of helical, disulfide-stabilized peptides

Structures and related properties of helical, disulfide-stabilized peptides

Trifluoroethanol effects on helix propensity and electrostatic interactions in the helical peptide from ribonuclease T1

The Structure of Calreticulin C-terminal Domain Is Modulated by Physiological Variations of Calcium Concentration

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Trifluoroethanol effects on helix propensity and electrostatic interactions in the helical peptide from ribonuclease T₁