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- Morozova, Ludmilla A, 1956-, et al.
(författare)
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Structural basis of the stability of a lysozyme molten globule.
- 1995
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Ingår i: Nature Structural Biology. - : Nature Publishing Group. - 1072-8368. ; 2:10, s. 871-875
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen exchange measurements on equine lysozyme show that amides in three of the four major helices of the native protein are significantly protected in a molten globule state formed at pH 2. The pattern of protection within the different helices, however, varies significantly. Examination of the pattern in the light of the native structure indicates that the side chains of the protected residues form a compact cluster within the core of the protein. We suggest that such a core is present in the molten globule state, indicating the existence of substantial native-like interactions between hydrophobic residues. The formation of clusters of this type during the early stages of folding could be crucial to directing polypeptide chains to their native structures.
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| 3. |
- Morozova-Roche, Ludmilla A, et al.
(författare)
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Structural characterisation and comparison of the native and A-states of equine lysozyme
- 1997
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 268:5, s. 903-921
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Tidskriftsartikel (refereegranskat)abstract
- Native state 1H NMR resonance assignments for 125 of the 129 residues of equine lysozyme have enabled measurement of the hydrogen exchange kinetics for over 60 backbone amide and three tryptophan indole hydrogen atoms in the native state. Native holo equine lysozyme hydrogen exchange protection factors are as large as 10(6), the most protected residues being located in elements of secondary structure. High exchange protection in the domain interface correlates with the binding of Ca2+ in this region. Equine lysozyme differs from most non-Ca2+ binding lysozymes in forming a highly populated partially folded state at low pH. The protein in this A-state at pH 2.0 has been found to bind 1-anilino-naphthalene-8-sulphonate with the enhancement of fluorescent intensity and blue shift in the spectral maximum characteristic of molten globules. NMR spectra indicate that the A-state is globally much less ordered than native equine lysozyme but does not contain significant regions of random coil structure. The amides most protected against hydrogen exchange in the A-state (protection factors up to 10(2) at 5 degrees C) correspond to residues of three of the four alpha-helices of the native state; the side-chains of these residues form a hydrophobic cluster that includes five aromatic residues. Circular dichroism and tryptophan fluorescence indicate that these residues are substantially more constrained than similar residues in "classical" molten globules. Taken together, the data suggest a model for the A-state of equine lysozyme in which a more ordered core is surrounded by a less ordered but still compact polypeptide chain.
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