Sequence environment of mutation affects stability and folding in collagen model peptides of osteogenesis imperfecta.
Osteogenesis imperfecta (OI), a disorder characterized by fragile bones, is often a consequence of missense mutations in type I collagen, which change one Gly in the repeating (Gly-Xaa-Yaa)(n) sequence to a larger amino acid. The impact of local environment and the identity of the residue replacing Gly were investigated using two sets of triple-helical peptides. Gly mutations in the highly stable (Pro-Hyp-Gly)(10) system are compared with mutations in T1-865 peptides where the mutation is located within a less stable natural collagen sequence. Replacement of a Gly residue by Ala, Ser, or Arg leads to significant triple-helical destabilization in both peptide systems. The loss of stability (ΔT(m) ) due to a Gly to Ala or Gly to Ser change was greater in the more rigid (Pro-Hyp-Gly)(10) peptides than in the T1-865 set, as expected. But the final T(m) values, which may be the more biologically meaningful parameters, were higher for the (Pro-Hyp-Gly)(10) mutation peptides than for the corresponding T1-865 mutation peptides. In both peptide environments, a Gly to Arg replacement prevented the formation of a fully folded triple-helix. Monitoring of folding by differential scanning calorimetry showed a lower stability species as well as the fully folded triple-helical molecules for T1-865 peptides with Gly to Ala or Ser replacements, and this lower stability species disappears as a function of time. The difficulty in propagation through a mutation site in T1-865 peptides may relate to the delayed folding seen in OI collagens and indicates a dependence of folding mechanism on the local sequence environment.
Department of Biochemistry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
Michael A
MA
Bryan
Haiming
H
Cheng
Barbara
B
Brodsky
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001120:Arginine / Q000737:chemistry / Q000235:genetics; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D024042:Collagen Type I / Q000737:chemistry* / Q000235:genetics*; D005998:Glycine / Q000737:chemistry / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010013:Osteogenesis Imperfecta / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017510:Protein Folding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D058767:Protein Unfolding; D013816:Thermodynamics
D024042:Collagen Type I; D010455:Peptides; C083881:(prolyl-hydroxylprolyl-glycine)10; D001120:Arginine; D005998:Glycine