Granule lattice protein 1 (Grl1p), an acidic, calcium-binding protein in Tetrahymena thermophila dense-core secretory granules, influences granule size, shape, content organization, and release but not protein sorting or condensation
Granule lattice protein 1 (Grl1p), an acidic, calcium-binding protein in Tetrahymena thermophila dense-core secretory granules, influences granule size, shape, content organization, and release but not protein sorting or condensation
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颗粒晶格蛋白1（Grl1p）是嗜热四膜虫密核分泌颗粒中的一种酸性钙结合蛋白，它影响颗粒的大小、形状、内容物组织和释放，但不影响蛋白质的分选或凝聚
DOI：
10.1083/jcb.135.6.1775
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发表时间：
1996-12-01
影响因子：
7.8
通讯作者：
Turkewitz, AP
中科院分区：
文献类型：
--
作者：
Chilcoat, ND;Melia, SM;Turkewitz, AP
嗜热四膜虫调节分泌颗粒的电子致密核心是由多种蛋白质组成的晶格。颗粒合成涉及一系列步骤，首先是蛋白质分选，然后是颗粒货物的浓缩和精确的几何组装。这些步骤可以在不同程度上由货物蛋白本身决定。在纤毛虫以及脊椎动物神经细胞和内分泌细胞中，一组突出的颗粒蛋白是酸性的、热稳定的，并且结合钙。我们专注于具有这些特征的蛋白质，称为颗粒晶格蛋白1（Grl1p），占总颗粒含量的16%，我们现在已经克隆了相应的基因。GRL 1的大核拷贝被破坏的突变体继续合成致密核心颗粒，但在调节蛋白质分泌方面存在缺陷。为了了解这种缺陷的性质，我们表征了突变体和野生型颗粒。在缺乏Grl1p的情况下，剩余颗粒蛋白的分选似乎正常，并且它们凝聚形成明确的核心，然而，凝聚的核心没有显示出可见的晶格，并且在大小和形状上与野生型明显不同。细胞分泌缺陷是由于异常颗粒核心在颗粒和质膜的胞吐融合后不能进行快速扩张和挤出所致。结果表明，分选，冷凝，和精确的颗粒组装是不同的要求Grl1p。
The electron-dense cores of regulated secretory granules in the ciliate Tetrahymena thermophila are crystal lattices composed of multiple proteins. Granule synthesis involves a series of steps beginning with protein sorting, followed by the condensation and precise geometric assembly of the granule cargo. These steps may to various degrees be determined by the cargo proteins themselves. A prominent group of granule proteins, in ciliates as well as in vertebrate neuronal and endocrine cells, are acidic, heat-stable, and bind calcium. We focused on a protein with these characteristics named granule lattice protein 1 (Grl1p), which represents 16% of total granule contents, and we have now cloned the corresponding gene. Mutants in which the macronuclear copies of GRL1 have been disrupted continue to synthesize dense-core granules but are nonetheless defective in regulated protein secretion. To understand the nature of this defect, we characterized mutant and wild-type granules. In the absence of Grl1p, the sorting of the remaining granule proteins appears normal, and they condense to form a well-defined core, However, the condensed cores do not demonstrate a visible crystalline lattice, and are notably different from wild type in size and shape. The cellular secretion defect arises from failure of the aberrant granule cores to undergo rapid expansion and extrusion after exocytic fusion of the granule and plasma membranes. The results suggest that sorting, condensation, and precise granule assembly are distinct in their requirements for Grl1p.