Transient UV Raman Spectroscopy Finds No Crossing Barrier between the Peptide α-Helix and Fully Random Coil Conformation

Lednev, Igor K.; Karnoup, Anton S.; Sparrow, Mark C.; Asher, Sanford A.

doi:10.1021/ja003381p

Cited by 87 publications

(193 citation statements)

References 26 publications

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“…Here, we report the use of infrared (IR) detected T-jump methods to investigate the folding kinetics of WT HP36 and the double Phe 3 Leu mutant. Nanosecond T-jump methods are well suited for studies of rapid folding reactions and have been applied to a range of systems (23)(24)(25)(26)(27)(28). The use of IR detection also provides an additional probe of the folding of HP36.…”

mentioning

confidence: 99%

Effect of modulating unfolded state structure on the folding kinetics of the villin headpiece subdomain

Brewer

Tang

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

148

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Equilibrium Fourier transform infrared (FTIR) and temperaturejump (T-jump) IR spectroscopic techniques were used to study the thermodynamics and kinetics of the unfolding and folding of the villin headpiece helical subdomain (HP36), a small three-helix protein. A double phenylalanine mutant (HP36 F47L, F51L) that destabilizes the hydrophobic core of this protein also was studied. The double mutant is less stable than wild type (WT) and has been shown to contain less residual secondary structure and tertiary contacts in its unfolded state. The relaxation kinetics after a T-jump perturbation were studied for both HP36 and HP36 F47L, F51L. Both proteins exhibited biphasic relaxation kinetics in response to a T-jump. The folding times for the WT (3.23 s at 60.2°C) and double phenylalanine mutant (3.01 s at 49.9°C) at the approximate midpoints of their thermal unfolding transitions were found to be similar. The folding time for the WT was determined to be 3.34 s at 49.9°C, similar to the folding time of the double phenylalanine mutant at that temperature. The double phenylalanine mutant, however, unfolds faster with an unfolding time of 3.01 s compared with 6.97 s for the WT at 49.9°C.protein folding ͉ Fourier transform IR ͉ temperature jump ͉ diffusion collision T he mechanism by which an unfolded polypeptide chain folds into its final native structure is still not fully understood, despite the obvious importance of the protein folding problem. In recent years there has been considerable interest in small single-domain proteins that fold quickly. These proteins provide attractive systems for computational and theoretical studies, and they are useful experimental models of the early steps in the assembly of more complicated folds. The helical subdomain derived from the villin headpiece, HP36, is a small three-helix structure found in the extreme C terminus of villin ( Fig. 1). Its modest size and helical structure suggest that it should fold rapidly, and this hypothesis has been independently confirmed by fluorescence-detected temperature-jump (T-jump) studies and NMR lineshape analysis (1-3). The helical subdomain is probably the smallest occurring natural sequence that has been shown to fold cooperatively. Its small size and very rapid folding have made it the focus of a large number of theoretical and computational studies (4-18).Residual structure and interactions in the unfolded state may play an important role in determining the rate of protein folding. Unfolded state structure might contribute to rapid folding by constraining and limiting the initial conformational search in the unfolded basin. Some models of folding postulate an important role for residual unfolded state structure. The diffusion collision model, for example, has been applied to rapidly folding helical proteins, and a key parameter in the model is the intrinsic stability of the individual microdomains (11,19,20). Although there have been a number of experimental studies of fast folding proteins, surprisingly little work has been reported that ...

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mentioning

confidence: 99%

Effect of modulating unfolded state structure on the folding kinetics of the villin headpiece subdomain

Brewer

Tang

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

148

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“…Helicity is an important characteristic of the polypeptide which can be measured experimentally [125][126][127][128]. It describes the fraction of amino acids in the polypeptide that are in the α-helix conformation.…”

Section: Helicity Of Alanine Polypeptidesmentioning

confidence: 99%

“…This system was chosen because it has been widely investigated both theoretically [15,[109][110][111][112][113][114][115][116][117][118][119][120][121][122][123][124] and experimentally [125][126][127][128] during the last five decades (for review see, e.g. [73,108,129,130]) and thus is a perfect system for testing a novel theoretical approach.…”

Section: Introductionmentioning

confidence: 99%

“…Experimentally, extensive studies of the helix-coil transition in polypeptides have been conducted [125][126][127][128]. In Ref.…”

Section: Introductionmentioning

confidence: 99%

“…In Refs. [126,127], UV resonance Raman spectroscopy was performed on the MABA-[A] 5 -[AAARA] 3 -ANH 2 peptide. Using circular dichroism methods, the dependence of helicity on temperature was measured.…”

Section: Introductionmentioning

confidence: 99%

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The sections in this article are Introduction Phenomenology Instrumentation Fundamental Applications Analytical Applications Biological Ultraviolet‐ R aman Studies Conclusions Acknowledgments

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Transient UV Raman Spectroscopy Finds No Crossing Barrier between the Peptide α-Helix and Fully Random Coil Conformation

Cited by 87 publications

References 26 publications

Effect of modulating unfolded state structure on the folding kinetics of the villin headpiece subdomain

Effect of modulating unfolded state structure on the folding kinetics of the villin headpiece subdomain

Theory of Phase Transitions in Polypeptides and Proteins

Ultraviolet R aman Spectrometry

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