MOLECULAR-CLONING AND CHARACTERIZATION OF THE CDNA CODING FOR C4B-BINDING PROTEIN, A REGULATORY PROTEIN OF THE CLASSICAL PATHWAY OF THE HUMAN-COMPLEMENT SYSTEM
MOLECULAR-CLONING AND CHARACTERIZATION OF THE CDNA CODING FOR C4B-BINDING PROTEIN, A REGULATORY PROTEIN OF THE CLASSICAL PATHWAY OF THE HUMAN-COMPLEMENT SYSTEM
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DOI：
10.1042/bj2300133
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发表时间：
1985-01-01
影响因子：
4.1
通讯作者：
REID, KBM
中科院分区：
文献类型：
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作者：
CHUNG, LP;BENTLEY, DR;REID, KBM
通过使用合成寡核苷酸作为探针，从肝脏 cDNA 文库中分离出含有编码人 C4b 结合蛋白的 cDNA 部分的质粒克隆。当与之前蛋白质水平的序列研究相结合时，C4b 结合蛋白的整个氨基酸序列可以从克隆 cDNA 的这项研究中预测出来 [Chung, Gagnon 和 Reid (1985) Mol.免疫学。 22, 427-435]，其中获得了超过55%的氨基酸序列，包括N端62个残基。分离的质粒克隆允许明确确定C4b结合蛋白序列中第32个氨基酸的密码子和3''非翻译区中第164个核苷酸之间的1717个核苷酸的cDNA序列。序列研究表明，血浆中发现的 C4b 结合蛋白的分泌形式由表观为 Mr 70,000 的链组成，其中包含 549 个氨基酸残基。蛋白质和cDNA序列检查结果显示该分子中至少存在两个多态性位点。一个位于44位，可以是谷氨酰胺或苏氨酸，另一个位于309位，可以是酪氨酸或组氨酸。 Northern 印迹分析表明 C4b 结合蛋白的 mRNA 约为。 2.5 千碱基长。 C4b 结合蛋白的 N 端 491 个氨基酸可分为 8 个内部同源区域，每个区域约 1 个。 60 个氨基酸长，可以通过每个区域中存在的四个半胱氨酸、一个色氨酸和几个其他保守残基进行比对。 C4b结合蛋白中的这些区域与据报道存在于补体酶因子B的Ba区域内的三个内部同源区域同源，并且还与非补体β2-糖蛋白I中发现的内部同源区域同源。
By using synthetic oligonucleotides as probes, plasmid clones containing portions of cDNA coding for human C4b-binding protein were isolated from a liver cDNA library. The entire amino acid sequence of the C4b-binding protein can be predicted from this study of the cloned cDNA when allied to a previous sequence study at the protein level [Chung, Gagnon and Reid (1985) Mol. Immunol. 22, 427-435], in which over 55% of the amino acid sequence, including the N-terminal 62 residues, was obtained. The plasmid clones isolated allowed the unambiguous determination of 1717 nucleotides of cDNA sequence between the codon for the 32nd amino acid in the sequence of C4b-binding protein and the 164th nucleotide in the 3'' non-translated region. The sequence studies show that the secreted form of C4b-binding protein, found in plasma, is composed of chains of apparent Mr 70,000 that contains 549 amino acid residues. Examination of the protein and cDNA sequence results show that there are at least two polymorphic sites in the molecule. One is at position 44, which can be glutamine or threonine, and the other is at position 309, which can be tyrosine or histidine. Northern-blot analysis indicated that the mRNA for C4b-binding protein is approx. 2.5 kilobases long. The N-terminal 491 amino acids of C4b-binding protein can be divided into eight internal homologous regions, each approx. 60 amino acids long, which can be aligned by the presence in each region of four half-cystine, one tryptophan and several other conserved residues. These regions in C4b-binding protein are homologous with the three internal-homology regions that have been reported to be present within the Ba region of the complement enzyme factor B and also to the internal-homology regions found in the non-complement .beta.2-glycoprotein I.