Proteolytic processing and Ca2+-binding activity of dense-core vesicle polypeptides in Tetrahymena.
Proteolytic processing and Ca2+-binding activity of dense-core vesicle polypeptides in Tetrahymena.
复制标题
四膜虫致密核心囊泡多肽的蛋白水解加工和 Ca2+ 结合活性。
DOI：
10.1091/mbc.9.2.497
复制
发表时间：
1998
影响因子：
3.3
通讯作者：
Turkewitz,AP
中科院分区：
文献类型：
--
作者：
Verbsky,JW;Turkewitz,AP
致密核心分泌囊泡的形成和排出取决于核心蛋白在组装和分散过程中的受控重排。纤毛虫嗜热四膜虫提供了一个可以研究其机制的简单系统。在这里，我们表明大部分核心由一组由五个前体蛋白水解衍生的多肽组成。这些氨基酸总体上几乎没有同一性，但预计具有结构相似性。此外，蛋白水解加工位点显着保守，表明特定的内切蛋白酶以及羧肽酶参与核心成熟。体外结合研究和序列分析表明多肽在体内结合钙。核心组装和胞外扩散是隔室特异性事件。两个可能的调节因素是蛋白水解加工和钙暴露。我们询问这些是否可能直接影响核心蛋白的构象。使用体外胰凝乳蛋白酶可及性测定的结果表明这些因素可以诱导连续的结构重排。多肽折叠的这种渐进变化可能是组装和快速胞外释放机制的基础。不同系统中的致密核心囊泡之间的相似性表明，类似的机制在此类细胞器中广泛存在。
Formation and discharge of dense-core secretory vesicles depend on controlled rearrangement of the core proteins during their assembly and dispersal. The ciliateTetrahymena thermophilaoffers a simple system in which the mechanisms may be studied. Here we show that most of the core consists of a set of polypeptides derived proteolytically from five precursors. These share little overall amino acid identity but are nonetheless predicted to have structural similarity. In addition, sites of proteolytic processing are notably conserved and suggest that specific endoproteases as well as carboxypeptidase are involved in core maturation. In vitro binding studies and sequence analysis suggest that the polypeptides bind calcium in vivo. Core assembly and postexocytic dispersal are compartment-specific events. Two likely regulatory factors are proteolytic processing and exposure to calcium. We asked whether these might directly influence the conformations of core proteins. Results using an in vitro chymotrypsin accessibility assay suggest that these factors can induce sequential structural rearrangements. Such progressive changes in polypeptide folding may underlie the mechanisms of assembly and of rapid postexocytic release. The parallels between dense-core vesicles in different systems suggest that similar mechanisms are widespread in this class of organelles.