Osteogenesis Imperfecta Missense Mutations in Collagen: Structural Consequences of a Glycine to Alanine Replacement at a Highly Charged Site

Abstract

Glycine is required as every third residue in the collagen triple-helix, and a missense mutation leading to the replacement of even one Gly in the repeating (Gly-Xaa-Yaa)n sequence by a larger residue leads to a pathological condition. Gly to Ala missense mutations are highly underrepresented in osteogenesis imperfecta (OI) and other collagen diseases, suggesting that the smallest replacement residue Ala might cause the least structural perturbation and mildest clinical consequences. The relatively small number of Gly to Ala mutation sites that do lead to OI must have some unusual features, such as greater structural disruption due to local sequence environment or location at a biologically important site. Here, peptides are used to model a severe OI case where a Gly to Ala mutation is found within a highly stabilizing Lys-Gly-Asp sequence environment. NMR, CD and DSC studies indicate this Gly to Ala replacement leads to a substantial loss in triple-helix stability and non-equivalence of the Ala residues in the three chains such that only one of the three Ala residues is capable of form a good backbone hydrogen bond. Examination of reported OI Gly to Ala mutations suggests preferential location at known collagen binding sites, and we propose that structural defects due to Ala replacements may lead to pathology when interfering with interactions.

Dynamic Water-Mediated Hydrogen Bonding in a Collagen Model Peptide

“…However, NMR data on G→A peptides suggest that the structural and dynamic perturbations are very sensitive to the local sequence context surrounding the mutation 21–24 , and that perturbations induced by the Gly to Ala mutation in the (POG) context deviate from those in the crystal environment. The NMR data indicates that the Gly to Ala substitutions lead to nonequivalence of the Ala residues in the three strands with one of the strands likely to form a good backbone hydrogen bond while the other two do not, and one strand having a very significant down field-shifted 1 H resonance relative to other two resonances in the HSQC spectra.…”

Molecular Level Insights on Collagen–Polyphenols Interaction Using Spin–Relaxation and Saturation Transfer Difference NMR

“…Nuclear Magnetic Resonance (NMR) based techniques on understanding the structure of collagen using collagen peptides is well established. [6][7][8] With reference to monitoring protein-ligand interactions there are two practical NMR approaches, 9,10 of which the primary approach focuses on protein, often requiring isotopic labelling (mostly 15 N label). Herein the chemical shift perturbations of protein resonances in the presence of a ligand are monitored using heteronuclear single-quantum correlation 4 (HSQC) spectroscopy and this enables an epitope mapping.…”

NMR Studies Demonstrate a Unique AAB Composition and Chain Register for a Heterotrimeric Type IV Collagen Model Peptide Containing a Natural Interruption Site

“…Triple-helical peptides have been extensively utilized as valuable models to investigate the stability, folding, dynamics, and molecular structure of collagen (15)(16)(17)(18)(19). Although the large majority of studies have been done on homotrimer collagen model peptides, a heterotrimer platform is needed to model collagens with more than one type of chain, such as type IV collagen.…”