Valli M, Zolezzi F, Mottes M, Antoniazzi F, Stanzial F, Tenni R, Pignatti P, Cetta G
Dipartimento di Biochimica, Università di Pavia, Italy.
Eur J Biochem. 1993 Oct 1;217(1):77-82. doi: 10.1111/j.1432-1033.1993.tb18220.x.
In this paper we describe a mild moderate form of osteogenesis imperfecta caused by a point mutation in COL1A1 which converted glycine 85 to valine. The valine substitution introduced into the triple-helical domain of type-I collagen a conformational perturbation causing susceptibility to digestive proteases. In fact, SDS/PAGE of pepsin-treated collagen showed the presence of a faint band, migrating between alpha 1(I) and alpha 2(I), both in the medium and in the cell layer. On trypsin digestion the band, a shortened form of alpha 1(I), had a melting temperature of 39.5 degrees C. If the triple-helical collagen was obtained after trypsin or chymotrypsin digestion of procollagen, two shortened bands were identified; the enzymes cleaved about 40% of the trimers. The mutant procollagen was normally secreted and processed in the extracellular matrix at a normal rate. When native type-I collagen was formed after dextran-sulfate incubation, only chains of normal length were found, suggesting that the fibroblast proteases did not recognize the alteration introduced by the mutation. The effects of glycine 85 to valine substitution are compared with those produced by a previously described arginine substitution of the same residue (Deak et al., 1991).
在本文中，我们描述了一种由COL1A1基因点突变引起的轻度至中度成骨不全症，该突变将甘氨酸85转变为缬氨酸。缬氨酸替代在I型胶原的三螺旋结构域中引入了构象扰动，导致对消化蛋白酶敏感。实际上，经胃蛋白酶处理的胶原的SDS/PAGE显示，在培养基和细胞层中均存在一条 faint 带，在α1（I）和α2（I）之间迁移。经胰蛋白酶消化后，该带（α1（I）的缩短形式）的解链温度为39.5摄氏度。如果在对前胶原进行胰蛋白酶或糜蛋白酶消化后获得三螺旋胶原，则可鉴定出两条缩短的带；这些酶切割了约40%的三聚体。突变前胶原通常以正常速率分泌并在细胞外基质中加工。在硫酸葡聚糖孵育后形成天然I型胶原时，仅发现正常长度的链，这表明成纤维细胞蛋白酶未识别出该突变引入的改变。将甘氨酸85至缬氨酸替代的效应与先前描述的同一残基的精氨酸替代所产生的效应进行了比较（Deak等人，1991年）。
