title: Destabilization of osteogenesis imperfecta collagen-like model peptides correlates with the identity of the residue replacing glycine.
abstract: Mutations resulting in replacement of one obligate Gly residue within the repeating (Gly-Xaa-Yaa)(n) triplet pattern of the collagen type I triple helix are the major cause of osteogenesis imperfecta (OI). Phenotypes of OI involve fragile bones and range from mild to perinatal lethal. In this study, host-guest triple-helical peptides of the form acetyl-(Gly-Pro-Hyp)(3)-Zaa-Pro-Hyp-(Gly-Pro-Hyp)(4)-Gly-Gly-amide are used to isolate the influence of the residue replacing Gly on triple-helix stability, with Zaa = Gly, Ala, Arg, Asp, Glu, Cys, Ser, or Val. Any substitution for Zaa = Gly (melting temperature, T(m) = 45 degrees C) results in a dramatic destabilization of the triple helix. For Ala and Ser, T(m) decreases to approximately 10 degrees C, and for the Arg-, Val-, Glu-, and Asp-containing peptides, T(m) < 0 degrees C. A Gly --> Cys replacement results in T(m) < 0 degrees C under reducing conditions but shows a broad transition (T(m) approximately 19 degrees C) in an oxidizing environment. Addition of trimethylamine N-oxide increases T(m) by approximately 5 degrees C per 1 M trimethylamine N-oxide, resulting in stable triple-helix formation for all peptides and allowing comparison of relative stabilities. The order of disruption of different Gly replacements in these peptides can be represented as Ala </= Ser < CPO(red) < Arg < Val < Glu </= Asp. The rank of destabilization of substitutions for Gly in these Gly-Pro-Hyp-rich homotrimeric peptides shows a significant correlation with the severity of natural OI mutations in the alpha1 chain of type I collagen.
authors.affiliation: Department of Biochemistry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
authors.forename: K
authors.initials: K
authors.lastname: Beck
authors.forename: V C
authors.initials: VC
authors.lastname: Chan
authors.forename: N
authors.initials: N
authors.lastname: Shenoy
authors.forename: A
authors.initials: A
authors.lastname: Kirkpatrick
authors.forename: J A
authors.initials: JA
authors.lastname: Ramshaw
authors.forename: B
authors.initials: B
authors.lastname: Brodsky
mesh_terms: D019943:Amino Acid Substitution; D002942:Circular Dichroism; D003094:Collagen / Q000737:chemistry / Q000378:metabolism*; D005998:Glycine / Q000378:metabolism*; D006801:Humans; D010013:Osteogenesis Imperfecta / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D010641:Phenotype; D011487:Protein Conformation; D013816:Thermodynamics
chemical_list: D010446:Peptide Fragments; D003094:Collagen; D005998:Glycine