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 (ΔTm) 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 Tm 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. © 2010 Wiley Periodicals, Inc.Biopolymers (Pept Sci) 96: 4–13, 2011.