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Urea Promotes Polyproline II Helix Formation:  Implications for Protein Denatured States
Biochemistry (2005)
  • Shelly J. Whittington, University of Kentucky
  • Brian W. Chellgren, University of Kentucky
  • Veronique M. Hermann, University of Kentucky
  • Trevor P Creamer, University of Kentucky
Abstract

It is commonly assumed that urea denatures proteins by promoting backbone disorder, resulting in random-coil behavior. Indeed, it has been demonstrated that highly denatured proteins obey random-coil statistics. However, the random-coil model is specified by the global geometric properties of a polymeric chain and does not preclude locally ordered backbone structure. While urea clearly disfavors a compact native structure, it is not clear that the resulting backbone conformations are disordered. Using circular dichroism (CD) spectroscopy, we demonstrate that urea promotes formation of left-handed polyproline II (PII) helical structures in both short peptides and denatured proteins. The observed increase in PII content is sequence-dependent. These data indicate that denatured states possess significant amounts of locally ordered backbone structure. It is time for the formulation of new denatured-state models that take into account the presence of significant local backbone structure. Criteria for such models are outlined.

Publication Date
2005
Citation Information
Shelly J. Whittington, Brian W. Chellgren, Veronique M. Hermann and Trevor P Creamer. "Urea Promotes Polyproline II Helix Formation:  Implications for Protein Denatured States" Biochemistry Vol. 44 Iss. 16 (2005)
Available at: http://works.bepress.com/trevor_creamer/7/