Dong Mingdong, Husale Sudhir, Sahin Ozgur
Rowland Institute at Harvard, Harvard University, Cambridge, MA 02142, USA.
Nat Nanotechnol. 2009 Aug;4(8):514-7. doi: 10.1038/nnano.2009.156. Epub 2009 Jun 28.
Proteins are dynamic molecular machines having structural flexibility that allows conformational changes. Current methods for the determination of protein flexibility rely mainly on the measurement of thermal fluctuations and disorder in protein conformations and tend to be experimentally challenging. Moreover, they reflect atomic fluctuations on picosecond timescales, whereas the large conformational changes in proteins typically happen on micro- to millisecond timescales. Here, we directly determine the flexibility of bacteriorhodopsin -- a protein that uses the energy in light to move protons across cell membranes -- at the microsecond timescale by monitoring force-induced deformations across the protein structure with a technique based on atomic force microscopy. In contrast to existing methods, the deformations we measure involve a collective response of protein residues and operate under physiologically relevant conditions with native proteins.
蛋白质是具有结构灵活性的动态分子机器，这种灵活性允许构象变化。目前用于测定蛋白质灵活性的方法主要依赖于对蛋白质构象中的热波动和无序性的测量，且往往在实验上具有挑战性。此外，它们反映的是皮秒时间尺度上的原子波动，而蛋白质中的大构象变化通常发生在微秒到毫秒时间尺度上。在这里，我们通过一种基于原子力显微镜的技术监测蛋白质结构上的力诱导变形，在微秒时间尺度上直接测定细菌视紫红质（一种利用光能将质子跨细胞膜转运的蛋白质）的灵活性。与现有方法不同，我们测量的变形涉及蛋白质残基的集体响应，并且是在天然蛋白质的生理相关条件下进行的。
