The flagellum of Trypanosoma brucei is a 20 micron-long organelle responsible for locomotion and cell morphogenesis. The flagellum attachment zone (FAZ) is a multi-protein complex whose function is to attach the flagellum to the cell body but also to guide cytokinesis. Cryo-transmission electron microscopy is a tool of choice to access the structure of the FAZ in a close-to-native state. However, because of the large dimension of the cell body, the whole FAZ cannot be structurally studied in situ at high resolution in 3D using classical transmission electron microscopy approaches. In the present work, cryo-scanning transmission electron tomography, a new method capable of investigating cryo-fixed thick biological samples, has been used to study whole T. brucei cells at the bloodstream stage. The method has been used to visualise and characterise the structure and organisation of the FAZ filament. It is composed of an array of cytoplasmic stick-like structures. These sticks are heterogeneously distributed between the posterior part and the anterior tip of the cell. This cryo-STET investigation provides new insights in the structure the FAZ filament. In combination with protein structure predictions, this work proposes a new model for the elongation of the FAZ.

中文翻译：

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布鲁氏锥虫鞭毛附着区的冷冻扫描透射电子层析成像原位结构分析

布氏锥虫的鞭毛是一个20微米长的细胞器，负责运动和细胞形态发生。鞭毛附着区（FAZ）是一种多蛋白复合物，其功能是将鞭毛附着于细胞体，并引导胞质分裂。低温透射电子显微镜是接近自然状态下访问FAZ结构的一种选择工具。但是，由于细胞体的尺寸较大，因此无法使用经典的透射电子显微镜方法以3D高分辨率对整个FAZ进行原位结构研究。在当前的工作中，低温扫描透射电子断层扫描是一种能够研究冷冻固定的厚生物样品的新方法，已被用于研究血液阶段的整个布鲁氏菌细胞。该方法已用于可视化和表征FAZ灯丝的结构和组织。它由一系列胞质棒状结构组成。这些棒不均匀地分布在细胞的后部和前尖端之间。这项低温STET研究为FAZ灯丝的结构提供了新的见识。结合蛋白质结构预测，这项工作提出了一种新的FAZ延伸模型。