title: Host-guest scale of left-handed polyproline II helix formation.
abstract: Despite the clear importance of the left-handed polyproline II (PPII) helical conformation in many physiologically important processes as well as its potential significance in protein unfolded states, little is known about the physical determinants of this conformation. We present here a scale of relative PPII helix-forming propensities measured for all residues, except tyrosine and tryptophan, in a proline-based host peptide system. Proline has the highest measured propensity in this system, a result of strong steric interactions that occur between adjacent prolyl rings. The other measured propensities are consistent with backbone solvation being an important component in PPII helix formation. Side chain to backbone hydrogen bonding may also play a role in stabilizing this conformation. The PPII helix-forming propensity scale will prove useful in future studies of the conformational properties of proline-rich sequences as well as provide insights into the prevalence of PPII helices in protein unfolded states.
authors.affiliation: Center for Structural Biology, Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536-0298, USA.
authors.forename: Adam L
authors.initials: AL
authors.lastname: Rucker
authors.forename: Cara T
authors.initials: CT
authors.lastname: Pager
authors.forename: Margaret N
authors.initials: MN
authors.lastname: Campbell
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Qualls
authors.forename: Trevor P
authors.initials: TP
authors.lastname: Creamer
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D010455:Peptides; C011083:polyproline