Fluctuation of an α-helix structure. Difference between the central and terminal portions

Nakanishi, Mamoru; Tsuboi, Masamichi; Ikegami, Akiba; Kanehisa, Minoru

doi:10.1016/0022-2836(72)90504-9

Cited by 39 publications

(17 citation statements)

References 14 publications

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“…Similar conclusions were made in our previous FTIR spectroscopic studies of the polyleucine-based peptide model P24 (Zhang et al, 1992a). These results are compatible with the suggestion that even very stable peptide helices exhibit frayed termini (Nakanishi et al, 1972).…”

Section: Discussionsupporting

confidence: 92%

Peptide Models of Helical Hydrophobic Transmembrane Segments of Membrane Proteins. 1. Studies of the Conformation, Intrabilayer Orientation, and Amide Hydrogen Exchangeability of Ac-K2-(LA)12-K2-Amide

Zhang¹,

Lewis²,

Henry³

et al. 1995

Biochemistry

117

121

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The secondary structure, amide hydrogen exchangeability, and intramembrane orientation of the hydrophobic peptide Ac-K2-(LA)12-K2-amide [(LA)12] were studied by a combination of circular dichroism (CD), Fourier transform infrared (FTIR), and proton nuclear magnetic resonance (1H NMR) spectroscopic techniques. All three techniques indicate that (LA)12 adopts predominantly helical conformations in various organic solvents, detergent micelles, and phospholipid bilayers. Also, attenuated total reflectance FTIR studies of oriented phospholipid bilayers demonstrate that (LA)12 is arranged with the long helical axis perpendicular to the bilayer plane. FTIR and 1H NMR studies of the exchangeability of the amide protons of (LA)12 indicate that in all media there are at least two populations of amide protons which exchange with the bulk solvent at markedly different rates. Moreover, the 1H NMR spectroscopic studies indicate that, in organic solvents and micellar dispersions, amide proton exchange rates decrease progressively from the N- or C-terminus of the peptide toward the central region. Our results are thus consistent with (LA)12 retaining a predominantly helical structure with so-called frayed ends in all media. The amide proton exchange studies also indicate that when (LA)12 is dispersed in lipid bilayers, the slowly exchanging population of amide protons is larger than that observed in organic solvents or in micellar dispersions and that most of that proton population is virtually unexchangeable. Such observations are consistent with the sequestration of the central regions of the peptide in the hydrophobic domains of the lipid bilayer. The CD and FTIR data indicate that although (LA)12 seems to retain conformations with a high alpha-helical content in all media examined, its conformation is sensitive to the composition of the surrounding medium, in contrast to the polyleucine-based analogues which have been studied previously. In particular, the FTIR spectroscopic data indicate that (LA)12 may exhibit an amide I absorption band between 1633 and 1639 cm-1 under some circumstances. The relative intensity of this band changes with the composition of the surrounding medium and its appearance has previously been correlated with the formation of 3(10)-helical structures [Miick et al. (1992) Nature 359, 653-655]. Thus (LA)12 may be interconverting between different helical conformations in response to changes in the physical properties of the medium in which the peptide is dispersed. Our results suggest that (LA)12 should serve as a good peptide model of hydrophobic, transmembrane helices which are conformationally sensitive to the properties of the lipid bilayer in which they reside.

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Section: Discussionsupporting

confidence: 92%

Peptide Models of Helical Hydrophobic Transmembrane Segments of Membrane Proteins. 1. Studies of the Conformation, Intrabilayer Orientation, and Amide Hydrogen Exchangeability of Ac-K2-(LA)12-K2-Amide

Zhang¹,

Lewis²,

Henry³

et al. 1995

Biochemistry

117

121

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“…the possibility of observing the transition to maximum helical content. At pH 4.6 the estimated helical content is >75%(22). The 13C shifts on the PGA sample of -93 880 M.W.were identical in direction and within 5 % in magnitude sf the 30 080 M.W.…”

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confidence: 78%

Carbon-13 Chemical Shifts Accompanying Helix Formation

Lyerla¹,

Barber²,

Freedman³

1973

Can. J. Biochem.

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Carbon-13 chemical shifts accompanying helix formation. Can. J. Biochem. 51,460-464 ( I973 ) .The heIix-coil transition in an aqueous solution of poHy-L-glutamic acid has been observed using 13C nuclear magnetic resonance. The transition from coil to helix results in pronounced deshielding of the carbowyl and C-a carbons of the polymer and a less dramatic shielding effect on the C-/3 carbon. These results are contrasted with the titration behavior of L-glutamic acid to delineate those shifts directly attributed to the secondary-structure change. The biological significance of this observation is supported by the 13C chemical shift differences observed for the 13C-enriched phenylalanyl residue $ in the free 1-15 amino-terminal peptide of ribonuclease ( RNase) and the 1-1 5 peptide: RNase S-protein complex. LYERLA, J. R., JR., BARBER, B. H., et FREEDMAN, M. H. Carbon-13 chemical shifts accompanying helix formation. Caw. 3. Biochem. 51,460-464 ( 1973 ) .Utilisant la rhsonance magnttique nucltaire du 13C, nous avoms sbsewrt la transition hClicepelote dans une solution aqueuse d'acide poly-L-glutamique. Par suite de la transition de pelsk 2 hClice, le carbone du groupemerat carbonyIe et le carbone alpha du polymhre subissent un dCmasquage pronomct tandis que 17effet sur le carbone beta est rnoins dramatique. Ces rCsuHtats sont opposts 2i ceux de Ia titration de l'acide L-glutamique pour dCcrire Bes dtplacements causCs directement par le changement de structure secomdaire. Laimportance biologique de ce rtsultat est confimte par les diffkrences entre les dCplasements chimiques du 'T Cue 1'on observe dais le rtsidu phtnylalanyl No. 8 enrichi de 13C du peptide libre 1-15 N-terminal de la ribonuq1Case (RNase ) et du complexe peptide 1-1 5 : RNase S-protCim. rraduit par Ie journal1

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“…There may be many kinds of relaxation modes in the helix-coil transition, some of which are not expected by the dynamics of the one-dimensional Ising model. For example, Fujiwara and Saito20 have proposed theoretically the mode having a long time scale associated with helix nucleation from a completely helical polypeptide in order to explain the results of the isotope exchange experiments by Ikegami et al 21 However, it is hard to think that the mode associated with coil nucleation has a much longer time scale than that associated with propagation step, as shown in our previous paper.19 Therefore, it is concluded that both approach-to-equilibrium measurement and NMR measurement observe the same mode of the relaxation of the helix-coil transition.…”

Section: Resultsmentioning

confidence: 99%