title: Secondary structure of a dynamic type I'beta-hairpin peptide.
abstract: A spontaneously folding beta-hairpin peptide (Lys-Lys-Tyr-Thr-Val-Ser-Ile-Asn-Gly-Lys-Lys-Ile-Thr-Val-Ser-Ile) and related cyclic (cyclo-Gly-Lys-Tyr-Ile-Asn-Gly-Lys-Ile-Ile-Asn) and linear (Ser-Ile-Asn-Gly-Lys) controls were studied to determine the effects of various factors on secondary structure. Secondary structure was evaluated using circular dichroism (CD) and 1D and 2D (1)H nuclear magnetic resonance (NMR). The effects of chemical modifications in the peptide and various solution conditions were investigated to determine their impact on peptide structure. The beta-hairpin peptide displayed a CD minimum at 216 nm and a TOCSY i + 1 - i + 2 and i + 2 -i + 3 interaction, confirming the expected structure. Using NMR alpha-proton (H(alpha)) chemical shifts, the extents of folding of the beta-hairpin and linear control were estimated to be 51 and 25% of the cyclic control (pH 4, 37 degrees C), which was taken to be maximally folded. Substitution of iso-aspartic acid for Asn reduced the secondary structure dramatically; substitution of aspartic acid for Asn also disrupted the structure. This result suggests that deamidation in unconstrained beta-turns may have adverse effects on secondary structure. N-terminal acetylation and extreme pH conditions also reduced structure, while the addition of methanol increased structure.
authors.affiliation: Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, KS 66047, USA.
authors.forename: C E
authors.initials: CE
authors.lastname: Stotz
authors.forename: R T
authors.initials: RT
authors.lastname: Borchardt
authors.forename: C R
authors.initials: CR
authors.lastname: Middaugh
authors.forename: T J
authors.initials: TJ
authors.lastname: Siahaan
authors.forename: D
authors.initials: D
authors.lastname: Vander Velde
authors.forename: E M
authors.initials: EM
authors.lastname: Topp
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D009842:Oligopeptides / Q000737:chemistry*; D010456:Peptides, Cyclic / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D009842:Oligopeptides; D010456:Peptides, Cyclic