Membrane cofactor protein of the complement system: alternative splicing of serine/threonine/proline-rich exons and cytoplasmic tails produces multiple isoforms that correlate with protein phenotype.
Membrane cofactor protein of the complement system: alternative splicing of serine/threonine/proline-rich exons and cytoplasmic tails produces multiple isoforms that correlate with protein phenotype.
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DOI：
10.1084/jem.174.1.93
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发表时间：
1991-07-01
期刊：
影响因子：
--
通讯作者：
Atkinson JP
中科院分区：
文献类型：
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作者：
Post TW;Liszewski MK;Adams EM;Tedja I;Miller EA;Atkinson JP
膜辅因子蛋白（MCP）是一种补体调节蛋白，在人细胞和细胞系上表达，作为两个相对广泛的物种，其Mr为58，000 - 68，000和48，000 - 56，000。先前报道的cDNA克隆的结构表明MCP是1型膜糖蛋白，是补体激活基因/蛋白簇的调节因子的成员。然而，它没有提供一个不寻常的MCP表型模式的解释。因此，在分析基因的同时，克隆并表征了另外的cDNA。鉴定了六种不同的MCP cDNA类。它们都编码相同的5'非翻译信号肽、4个SCR、跨膜结构域和碱性氨基酸锚。然而，它们在细胞外丝氨酸/苏氨酸/脯氨酸（STP）富集区、重O-糖基化位点和细胞质尾区的长度和组成上不同。MCP基因的分析表明，在cDNA结构的变化是选择性剪接的结果。外周血细胞和细胞系主要表达六种亚型中的四种。这些变化的存在或不存在的STP-丰富的15个氨基酸（STPB）的部分，并通过使用两个胞质结构域之一。聚合酶链反应，北方印迹，转染分析表明，MCP cDNA亚型与STPB的优势与高分子量蛋白质表型相关，而优势的亚型没有STPB与低分子量表型相关。在单个细胞中表达四种不同的蛋白质种类，具有可变的富含STP的区域和胞质尾，代表了使用选择性剪接来提供哺乳动物蛋白质中的可变性的有趣实例。
Membrane cofactor protein (MCP) is a complement regulatory protein that is expressed on human cells and cell lines as two relatively broad species with Mr of 58,000-68,000 and 48,000-56,000. The structure of a previously reported cDNA clone indicated that MCP was a type 1 membrane glycoprotein and a member of the regulators of complement activation gene/protein cluster. However, it did not provide an explanation for the unusual phenotypic pattern of MCP. Therefore, in parallel with an analysis of the gene, additional cDNAs were cloned and characterized. Six different MCP cDNA classes were identified. All encode the same 5' untranslated signal peptide, four SCRs, transmembrane domain, and basic amino acid anchor. However, they differ in the length and composition of an extracellular serine/threonine/proline (STP)-rich area, a site of heavy O-glycosylation, and cytoplasmic tail. Analysis of the MCP gene demonstrated that the variation in cDNA structure was a result of alternative splicing. Peripheral blood cells and cell lines predominantly expressed four of the six isoforms. These varied by the presence or absence of an STP-rich segment of 15 amino acids (STPB) and by the use of one of two cytoplasmic domains. Analysis by polymerase chain reaction, Northern blots, and transfection indicated that the predominance of MCP cDNA isoforms with STPB correlated with the high molecular weight protein phenotype, while the predominance of isoforms without STPB correlated with the lower molecular weight phenotype. The expression in a single cell of four distinct protein species with variable STP-rich regions and cytoplasmic tails represents an interesting example of the use of alternative splicing to provide variability in a mammalian protein.