کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2188348 1096163 2007 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Tuning λ6–85 Towards Downhill Folding at its Melting Temperature
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی بیولوژی سلول
پیش نمایش صفحه اول مقاله
Tuning λ6–85 Towards Downhill Folding at its Melting Temperature
چکیده انگلیسی

The five-helix bundle λ6–85* is a fast two-state folder. Several stabilized mutants have been reported to fold kinetically near-downhill or downhill. These mutants undergo a transition to two-state folding kinetics when heated. It has been suggested that this transition is caused by increased hydrophobicity at higher temperature. Here we investigate two histidine-containing mutants of λ6–85* to see if a weaker hydrophobic core can extend the temperature range of downhill folding. The very stable λHA is the fastest-folding lambda repressor to date (kf− 1 ≈ kobs− 1 = 2.3 μs at 44 °C). It folds downhill at low temperature, but transits back to two-state folding at its unfolding midpoint. λHG has a weakened hydrophobic core. It is less stable than some slower folding mutants of λ6–85*, and it has more exposed hydrophobic surface area in the folded state. This mutant nonetheless folds very rapidly, and has the non-exponential folding kinetics of an incipient downhill folder even at the unfolding midpoint (km− 1 ≈ 2 μs, ka− 1 = 15 μs at 56 °C). We also compare the thermodynamic melting transition of λHG with the nominal two-state folding mutant λQG, which has a similar melting temperature. Unlike λQG, λHG yields fluorescence wavelength-dependent cooperativities and probe-dependent melting temperatures. This result combined with previous work shows that the energy landscapes of lambda repressor mutants support all standard folding mechanisms.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Biology - Volume 370, Issue 3, 13 July 2007, Pages 574–584
نویسندگان
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