F actin bundles in Drosophila bristles. I. Two filament cross-links are involved in bundling.
F actin bundles in Drosophila bristles. I. Two filament cross-links are involved in bundling.
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DOI：
10.1083/jcb.130.3.629
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发表时间：
1995-08
期刊：
影响因子：
--
通讯作者：
Guild GM
中科院分区：
文献类型：
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作者：
Tilney LG;Tilney MS;Guild GM
果蝇刚毛的横切面显示7-11个近圆形的、与质膜相关的肌动蛋白丝束。这些细丝是六边形堆积的，在纵截面上，它们在1.1和1.0视图中都显示出12 nm的周期性。从早期的研究中，这种周期性可归因于交联，并表明细丝是最大程度交联的，烧焦的突变体也有7-11束，但束较小，扁平，束内的细丝是随机堆积的（不是六边形）;在纵向截面中没有检测到周期性。另一个突变体，分叉的（f36 a），也有7-11束，但即使束是非常小的，其中的细丝是六角形包装和显示12纳米的周期性在纵向截面。单叉双突变体缺少丝束。因此，在相邻的肌动蛋白丝之间至少有两种交联。为什么两种交联是必要的提示可以通过研究刚毛的形成来收集。刚毛在里面只有微管。在发育稍晚时，出现肌动蛋白丝。在早期阶段，纤维束中的纤维是随机堆积的。随后，纤维束中的纤维变成六边形排列，并最大程度地交联。我们认为，分叉蛋白可能是必要的早期发展，以捆绑在一起的细丝束，使他们可以随后拉链在一起的fascin（烧焦的基因产物）。
Transverse sections though Drosophila bristles reveal 7-11 nearly round, plasma membrane-associated bundles of actin filaments. These filaments are hexagonally packed and in a longitudinal section they show a 12-nm periodicity in both the 1.1 and 1.0 views. From earlier studies this periodicity is attributable to cross-links and indicates that the filaments are maximally cross-linked, singed mutants also have 7-11 bundles, but the bundles are smaller, flattened, and the filaments within the bundles are randomly packed (not hexagonal); no periodicity can be detected in longitudinal sections. Another mutant, forked (f36a), also has 7-11 bundles but even though the bundles are very small, the filaments within them are hexagonally packed and display a 12-nm periodicity in longitudinal section. The singed-forked double mutant lacks filament bundles. Thus there are at least two species of cross-links between adjacent actin filaments. Hints of why two species of cross-links are necessary can be gleaned by studying bristle formation. Bristles sprout with only microtubules within them. A little later in development actin filaments appear. At early stages the filaments in the bundles are randomly packed. Later the filaments in the bundles become hexagonally packed and maximally cross-linked. We consider that the forked proteins may be necessary early in development to tie the filaments together in a bundle so that they can be subsequently zippered together by fascin (the singed gene product).