Petersen T E, Thøgersen H C, Skorstengaard K, Vibe-Pedersen K, Sahl P, Sottrup-Jensen L, Magnusson S
Proc Natl Acad Sci U S A. 1983 Jan;80(1):137-41. doi: 10.1073/pnas.80.1.137.
Approximately one-half of the amino acid sequence (911 amino acid residues out of 1,880 expected) for bovine plasma fibronectin (cold-insoluble globulin) has been determined. Three types of internal homology were identified, showing that a number of partial gene duplications (multiplications) have occurred during the evolution of this protein. Digestion of fibronectin with plasmin results in major fragments with molecular masses of 29, 170, 23, and 6 kilodaltons (kDal). The NH(2)-terminal 29-kDal fragment consists of 259 residues ordered as five mutually homologous domains (type I homology) with two disulfide bonds in each domain. The 170-kDal fragment shows two to three bands after NaDodSO(4) gel electrophoresis, indicating heterogeneity. This fragment contains the gelatin binding site and the strong heparin binding site present in fibronectin. Digestion of the 170-kDal fragment with chymotrypsin liberates a 45-kDal fragment that also binds to gelatin. This fragment contains at least one domain of type I homology and two domains of type II homology. Further digestion of the 170-kDal fragment with chymotrypsin results in the formation of a 30-kDal fragment that retains the heparin binding activity. This fragment contains sequences constituting type III homology. The 23-kDal fragment consists of 178 residues having three domains of type I homology. The 6-kDal fragment consists of two identical peptides of 26 residues, and these two peptides are linked to each other by two disulfide bonds that form the interchain bridges. Another one of the peptides for which the sequence was determined links the COOH-terminus of the 29-kDal fragment to the NH(2)-terminus of the 170-kDal fragment. This and the fact that the COOH-terminal residue of the 6-kDal fragment is a glutamic acid residue order the four plasmin-digestion fragments as 29-, 170-, 23-, and 6-kDal in the intact fibronectin molecule.
牛血浆纤连蛋白（冷不溶性球蛋白）大约一半的氨基酸序列（预期的1880个氨基酸残基中的911个）已被确定。鉴定出三种类型的内部同源性，表明在该蛋白质的进化过程中发生了一些部分基因重复（倍增）。纤连蛋白用纤溶酶消化产生分子量为29、170、23和6千道尔顿（kDal）的主要片段。NH₂末端的29-kDal片段由259个残基组成，排列成五个相互同源的结构域（I型同源性），每个结构域中有两个二硫键。170-kDal片段在NaDodSO₄凝胶电泳后显示两到三条带，表明存在异质性。该片段包含纤连蛋白中的明胶结合位点和强肝素结合位点。用胰凝乳蛋白酶消化170-kDal片段可释放出一个也能与明胶结合的45-kDal片段。该片段包含至少一个I型同源性结构域和两个II型同源性结构域。用胰凝乳蛋白酶进一步消化170-kDal片段会形成一个保留肝素结合活性的30-kDal片段。该片段包含构成III型同源性的序列。23-kDal片段由178个残基组成，具有三个I型同源性结构域。6-kDal片段由两个26个残基的相同肽段组成，这两个肽段通过形成链间桥的两个二硫键相互连接。另一个已确定序列的肽段将29-kDal片段的COOH末端与170-kDal片段的NH₂末端相连。这以及6-kDal片段的COOH末端残基是谷氨酸残基这一事实，将完整纤连蛋白分子中的四个纤溶酶消化片段按29-、170-、23-和6-kDal的顺序排列。
