J. Biol. Chem., Vol. 262, Issue 10, 4445-4451, Apr, 1987
A structural mutation of the collagen alpha 1(I)CB7 peptide in lethal perinatal osteogenesis imperfecta
JF Bateman, T Mascara, D Chan and WG Cole
Structurally abnormal type I collagen was identified in the dermis, bone,
and cultured fibroblasts obtained from a baby with lethal perinatal
osteogenesis imperfecta. Two-dimensional gel electrophoresis of the CNBr
peptides demonstrated that the alpha 1(I)CB7 peptide from the alpha
1(I)-chain of type I collagen existed in a normal form and a mutant form
with a more basic charge distribution. This heterozygous peptide defect was
not detected in the collagens from either parent. The defect was localized
to a 224-residue region at the NH2 terminus of the alpha 1(I)CB7 peptide by
mammalian collagenase digestion. Analysis of unhydroxylated collagens
produced in cell culture indicated that the mutant alpha 1(I)CB7 migrated
faster on electrophoresis suggesting that the abnormality may be a small
deletion or a mutation that alters sodium dodecyl sulfate binding. The
post-translational hydroxylation of lysine residues was increased in the
CB7 peptide and also in peptides CB3 and CB8 which are toward the NH2
terminus of the alpha 1(I)-chain. The COOH-terminal CB6 peptide was
normally hydroxylated. These findings support the proposal that the lysine
overhydroxylation resulted from a perturbation of helix propagation from
the COOH to NH2 terminus of the collagen trimer caused by the structural
defect in alpha 1(I)CB7.