沿DNA運(yùn)動(dòng)的蛋白機(jī)器如DNA聚合酶和解旋酶,，必將遭遇與特定點(diǎn)發(fā)生相互作用的其他所結(jié)合的蛋白,。Finkelstein等人利用由標(biāo)記的DNA構(gòu)成的納米“簾子”來確定這種結(jié)合蛋白是否干涉細(xì)菌DNA轉(zhuǎn)位酶RecBCD的活性。他們發(fā)現(xiàn),，這種酶非常“強(qiáng)健”,，在它們被取代之前能將蛋白在非特定點(diǎn)上推動(dòng)數(shù)千個(gè)堿基對的距離。（生物谷Bioon.com）
生物谷推薦原文出處：
Nature doi:10.1038/nature09561
Single-molecule imaging reveals mechanisms of protein disruption by a DNA translocase
Ilya J. Finkelstein,Mari-Liis Visnapuu& Eric C. Greene
In physiological settings, nucleic-acid translocases must act on substrates occupied by other proteins, and an increasingly appreciated role of translocases is to catalyse protein displacement from RNA and DNA1, 2, 3, 4. However, little is known regarding the inevitable collisions that must occur, and the fate of protein obstacles and the mechanisms by which they are evicted from DNA remain unexplored. Here we sought to establish the mechanistic basis for protein displacement from DNA using RecBCD as a model system. Using nanofabricated curtains of DNA and multicolour single-molecule microscopy, we visualized collisions between a model translocase and different DNA-bound proteins in real time. We show that the DNA translocase RecBCD can disrupt core RNA polymerase, holoenzymes, stalled elongation complexes and transcribing RNA polymerases in either head-to-head or head-to-tail orientations, as well as EcoRIE111Q, lac repressor and even nucleosomes. RecBCD did not pause during collisions and often pushed proteins thousands of base pairs before evicting them from DNA. We conclude that RecBCD overwhelms obstacles through direct transduction of chemomechanical force with no need for specific protein–protein interactions, and that proteins can be removed from DNA through active disruption mechanisms that act on a transition state intermediate as they are pushed from one nonspecific site to the next.
