Journal article
Urea unfolding of peptide helices as a model for interpreting protein unfolding
Proceedings of the National Academy of Sciences - PNAS, Vol.92(1), pp.185-189
01/03/1995
DOI: 10.1073/pnas.92.1.185
PMCID: PMC42842
PMID: 7816813
Abstract
To provide a model system for understanding how the unfolding of protein alpha-helices by urea contributes to protein denaturation, urea unfolding was measured for a homologous series of helical peptides with the repeating sequence Ala-Glu-Ala-Ala-Lys-Ala and chain lengths varying from 14 to 50 residues. The dependence of the helix propagation parameter of the Zimm-Bragg model for helix-coil transition theory (s) on urea molarity ([urea]) was determined at 0 degree C with data for the entire set of peptides, and a linear dependence of In s on [urea] was found. The results were fitted by the binding-site model and by the solvent-exchange model for the interaction of urea with the peptides. Each of these thermodynamic models is able to describe the data quite well and we are not able to discern any difference between the ability of each model to fit the data. Thus a linear relation, ln s = ln s0 - (m/RT).[urea], fits the data for alpha-helix unfolding, just as others have found for protein unfolding. When the m value determined here for alpha-helix unfolding is multiplied by the number of helical residues in partly helical protein molecules, the resulting values agree within a factor of 2 with observed m values for these proteins. This result indicates that the interaction between urea and peptide groups accounts for a major part of the denaturing action of urea on proteins, as predicted earlier by some model studies with small molecules.
Details
- Title: Subtitle
- Urea unfolding of peptide helices as a model for interpreting protein unfolding
- Creators
- J M Scholtz - Stanford UniversityD Barrick - Stanford University School of MedicineE J York - Stanford University School of MedicineJ M Stewart - Stanford University School of MedicineR L Baldwin - Stanford University School of Medicine
- Resource Type
- Journal article
- Publication Details
- Proceedings of the National Academy of Sciences - PNAS, Vol.92(1), pp.185-189
- DOI
- 10.1073/pnas.92.1.185
- PMID
- 7816813
- PMCID
- PMC42842
- NLM abbreviation
- Proc Natl Acad Sci U S A
- ISSN
- 0027-8424
- eISSN
- 1091-6490
- Publisher
- National Academy of Sciences
- Language
- English
- Date published
- 01/03/1995
- Academic Unit
- Research Administration; Pharmaceutical Sciences and Experimental Therapeutics; Biochemistry and Molecular Biology; Chemistry
- Record Identifier
- 9984288718302771
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