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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Proprotein convertases in amphioxus: predicted structure and expression of proteases SPC2 and SPC3.
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Proprotein convertases in amphioxus: predicted structure and expression of proteases SPC2 and SPC3.

机译：两栖动物中的前蛋白转化酶：蛋白酶SPC2和SPC3的预测结构和表达。

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SPC2 and SPC3 are two members of a family of subtilisin-related proteases which play essential roles in the processing of prohormones into their mature forms in the pancreatic B cell and many other neuroendocrine cells. To investigate the phylogenetic origins and evolutionary functions of SPC2 and SPC3 we have identified and cloned cDNAs encoding these enzymes from amphioxus (Branchiostoma californiensis), a primitive chordate. The amino acid sequence of preproSPC2 contains 689 aa and is 71% identical to human SPC2. In contrast, amphioxus prproSPC3 consists of 774 aa and exhibits 55% identity to human SPC3. These results suggest that the primary structure of SPC2 has been more highly conserved during evolution than that of SPC3. To further investigate the function(s) of SPC2 and SPC3 in amphioxus, we have determined the regional expression of these genes by using a reverse transcriptase-linked polymerase chain reaction (RT-PCR) assay. Whole amphioxus was dissected longitudinally into four equal-length segments and RNA was extracted. Using RT-PCR to simultaneously amplify SPC2 and SPC3 DNA fragments, we found that the cranial region (section 1) expressed equal amounts of SPC2 and SPC3 mRNAs, whereas in the caudal region (section 4) the SPC2-to-SPC3 ratio was 5:1. In the mid-body sections 2 and 3 the SPC2-to-SPC3 ratio was 1:5. By RT-PCR we also determined that amphioxus ILP, a homologue of mammalian insulin/insulin-like growth factor, was expressed predominately in section 3. These results suggest that the relative levels of SPC2 and SPC3 mRNAs are specifically regulated in various amphioxus tissues. Furthermore, the ubiquitous expression of these mRNAs in the organism indicates that they are involved in the processing of other precursor proteins in addition to proILP.
机译：SPC2和SPC3是枯草杆菌蛋白酶相关蛋白酶家族的两个成员，它们在胰腺B细胞和许多其他神经内分泌细胞中将激素原转化为成熟形式中起着至关重要的作用。为了研究SPC2和SPC3的系统发生起源和进化功能，我们从原始的绒毛虫-双歧杆菌（Branchiostoma californiensis）中鉴定并克隆了编码这些酶的cDNA。 preproSPC2的氨基酸序列包含689个氨基酸，与人SPC2的同源性为71％。相比之下，双歧杆菌prproSPC3由774氨基酸组成，与人SPC3具有55％的同一性。这些结果表明，SPC2的一级结构在进化过程中比SPC3的保守性更高。为了进一步研究SPC2和SPC3在文昌鱼中的功能，我们已经通过使用逆转录酶联聚合酶链反应（RT-PCR）分析确定了这些基因的区域表达。将整个两栖动物纵向切成四个等长的片段，并提取RNA。使用RT-PCR同时扩增SPC2和SPC3 DNA片段，我们发现颅骨区域（第1部分）表达了相等数量的SPC2和SPC3 mRNA，而在尾巴区域（第4部分）中，SPC2与SPC3的比例为5 ：1。在车身中部2和3中，SPC2与SPC3的比例为1：5。通过RT-PCR，我们还确定了在第3节中主要表达了哺乳动物胰岛素/胰岛素样生长因子的同源物-双歧杆菌ILP。这些结果表明，SPC2和SPC3 mRNA的相对水平在各种双歧杆菌组织中均受到特定调节。此外，这些mRNA在生物体中的普遍表达表明它们除了proILP外还参与其他前体蛋白的加工。

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