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Title: Altered triple helical structure of type I procollagen in lethal perinatal osteogenesis imperfecta. Author: Bonadio J, Holbrook KA, Gelinas RE, Jacob J, Byers PH. Journal: J Biol Chem; 1985 Feb 10; 260(3):1734-42. PubMed ID: 2981871. Abstract: Cultured dermal fibroblasts from an infant with the lethal perinatal form of osteogenesis imperfecta (type II) synthesize normal and abnormal forms of type I procollagen. The abnormal type I procollagen molecules are excessively modified during their intracellular stay, have a lower than normal melting transition temperature, are secreted at a reduced rate, and form abnormally thin collagen fibrils in the extracellular matrix in vitro. Overmodification of the abnormal type I procollagen molecules was limited to the NH2-terminal three-fourths of the triple helical domain. Two-dimensional mapping of modified and unmodified alpha chains of type I collagen demonstrated neither charge alterations nor large insertions or deletions in the region of alpha 1(I) and alpha 2(I) in which overmodification begins. Both the structure and function of type I procollagen synthesized by cells from the parents of this infant were normal. The simplest interpretation of the results of this study is that the osteogenesis imperfecta phenotype arose from a new dominant mutation in one of the genes encoding the chains of type I procollagen. Given the requirement for glycine in every third position of the triple helical domain, the mutation may represent a single amino acid substitution for a glycine residue. These findings demonstrate further heterogeneity in the biochemical basis of osteogenesis imperfecta type II and suggest that the nature and location of mutations in type I procollagen may determine phenotypic variation.[Abstract] [Full Text] [Related] [New Search]