Subunit organization and structure of lon protease

扫描电子显微镜(STEM) 已应用于确定 酶，离子蛋白水解酶，一种重要的能量依赖的蛋白酶 负责细胞质蛋白质的降解。尽管 Lon蛋白水解酶的序列已知，其结构尚未确定 下定决心。在首先刻画了 通过阴性染色制备，将该蛋白应用于 铜栅支撑的超薄碳膜及其冷冻 变成液态乙烷。样品被冷冻干燥并在Low中成像 提供定量质量图的剂量环状暗场STEM 由此计算出蛋白质的相对分子质量分布 可以确定组件。质量分布被发现为 是双峰，揭示了八聚体和四聚体的存在。在 未来，将尝试本地化的衬底 通过对大量低剂量图像进行平均化处理来检测酶的活性。

Scanning transmission electron microscopy (STEM) has been applied to determine the subunit organization of the enzyme, lon protease, an important energy-dependent protease that is responsible for cytoplasmic protein degradation. Although the sequence of lon protease is known, its structure has not yet been determined. After first characterizing the homogeneity of the preparations by negative staining, the protein was applied to ultrathin carbon films supported on copper grids and plunge frozen into liquid ethane. Samples were freeze-dried and imaged in low dose annular dark-field STEM to provide quantitative mass maps from which the molecular weight distribution of the protein assemblies could be determined. The mass distribution was found to be bimodal revealing the existence of octamers and tetramers. In the future, attempts will be made to localize the substrate of the enzyme by averaging large numbers of low-dose images.