Levy Y Y, Lai E Y, Remillard S P, Heintzelman M B, Fulton C
Department of Biology, Brandeis University, Waltham, Massachusetts 02254-9110, USA.
Cell Motil Cytoskeleton. 1996;33(4):298-323. doi: 10.1002/(SICI)1097-0169(1996)33:4<298::AID-CM6>3.0.CO;2-5.
Centrin, a approximately or equal to 20 kDa calcium-binding protein also known as caltractin, is a component of centrosome-associated algal flagellar roots capable of calcium-mediated contraction, and is also found in the centrosomes of vertebrate cells. Our analysis of a centrin gene from a protist, the amoeboflagellate Naegleria gruberi, reveals conserved features that distinguish centrins from calmodulin. Antibodies to bacterially expressed Naegleria centrin, which also recognize yeast Cdc31p, were employed to localize centrin immunoreactivity in selected organisms possessing specialized microtubule-organizing centers (MTOCs) or accessory structures. There is a striking morphological diversity of such structures. In the simplest associations, as found in Naegleria flagellates and vertebrates tracheal epithelium, centrin is intimately associated with the cylinder of the basal bodies. In cells with unfocused mitotic spindles, Naegleria amoebae and onion root tips, no localization of centrin was detected. In Dictyostelium discoideum and Saccharomyces cerevisiae, which lack centrioles, centrin immunoreactivity was observed as punctate cytoplasmic bodies but not associated with spindle pole MTOCs. In Paramecium multimicronucleatum, centrin immunoreactivity is localized to the infraciliary lattice, previously shown to exhibit calcium-mediated contraction. In Vorticella microstoma, known for the calcium-induced rapid contraction of its stalk, centrin immunoreactivity is localized to the contractile spasmoneme and myonemes. Similar antigens from Paramecium and Vorticella are detected by anti-centrin and anti-spasmin. The pattern of localization of centrin immunoreactivity supports the conjecture that a contractile system involving centrin, initially associated with centriolar structures, was recruited during evolution to build specialized organelles in different organisms and cell types.
中心蛋白是一种分子量约为20 kDa的钙结合蛋白，也被称为钙牵蛋白，是中心体相关的藻类鞭毛根的组成部分，能够进行钙介导的收缩，同时也存在于脊椎动物细胞的中心体中。我们对原生生物变形鞭毛虫格氏耐格里虫的一个中心蛋白基因进行分析，发现了一些保守特征，这些特征将中心蛋白与钙调蛋白区分开来。利用针对细菌表达的耐格里虫中心蛋白（该蛋白也能识别酵母Cdc31p）制备的抗体，在具有特殊微管组织中心（MTOC）或附属结构的特定生物体中定位中心蛋白免疫反应性。这些结构在形态上具有显著的多样性。在耐格里虫鞭毛虫和脊椎动物气管上皮中发现的最简单的关联中，中心蛋白与基体的圆柱体紧密相关。在有弥散有丝分裂纺锤体的细胞，如耐格里虫变形虫和洋葱根尖中，未检测到中心蛋白的定位。在缺乏中心粒的盘基网柄菌和酿酒酵母中，中心蛋白免疫反应性表现为点状细胞质体，但不与纺锤极MTOC相关。在多核草履虫中，中心蛋白免疫反应性定位于纤毛下晶格，先前已证明该晶格能进行钙介导的收缩。在以其柄部钙诱导快速收缩而闻名的小口钟虫中，中心蛋白免疫反应性定位于收缩性肌丝和肌原纤维。抗中心蛋白和抗肌丝蛋白能检测到来自草履虫和钟虫的类似抗原。中心蛋白免疫反应性的定位模式支持了这样一种推测，即涉及中心蛋白的收缩系统最初与中心粒结构相关，在进化过程中被招募来构建不同生物体和细胞类型中的特殊细胞器。
