Location of glycine mutations within a bacterial collagen protein affects degree of disruption of triple-helix folding and conformation.
The hereditary bone disorder osteogenesis imperfecta is often caused by missense mutations in type I collagen that change one Gly residue to a larger residue and that break the typical (Gly-Xaa-Yaa)(n) sequence pattern. Site-directed mutagenesis in a recombinant bacterial collagen system was used to explore the effects of the Gly mutation position and of the identity of the residue replacing Gly in a homogeneous collagen molecular population. Homotrimeric bacterial collagen proteins with a Gly-to-Arg or Gly-to-Ser replacement formed stable triple-helix molecules with a reproducible 2 °C decrease in stability. All Gly replacements led to a significant delay in triple-helix folding, but a more dramatic delay was observed when the mutation was located near the N terminus of the triple-helix domain. This highly disruptive mutation, close to the globular N-terminal trimerization domain where folding is initiated, is likely to interfere with triple-helix nucleation. A positional effect of mutations was also suggested by trypsin sensitivity for a Gly-to-Arg replacement close to the triple-helix N terminus but not for the same replacement near the center of the molecule. The significant impact of the location of a mutation on triple-helix folding and conformation could relate to the severe consequences of mutations located near the C terminus of type I and type III collagens, where trimerization occurs and triple-helix folding is initiated.
Department of Biochemistry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
Haiming
H
Cheng
Shayan
S
Rashid
Zhuoxin
Z
Yu
Ayumi
A
Yoshizumi
Eileen
E
Hwang
Barbara
B
Brodsky
D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003094:Collagen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005998:Glycine / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D013297:Streptococcus pyogenes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; C423453:Scl2 protein, Streptococcus; D003094:Collagen; D005998:Glycine