DNA-Protein Interactions Unit, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, BS8 1TD, UK.
Nucleic Acids Res. 2009 Nov;37(21):7219-30. doi: 10.1093/nar/gkp794.
To cleave DNA, the single polypeptide restriction-modification enzyme LlaGI must communicate between a pair of indirectly repeated recognition sites. We demonstrate that this communication occurs by a 1-dimensional route, namely unidirectional dsDNA loop translocation rightward of the specific recognition sequence 5'-CTnGAyG-3' as written (where n is either A, G, C or T and y is either C or T). Motion across thousands of base pairs is catalysed by the helicase domain and requires the hydrolysis of 1.5-2 ATP per base pair. DNA loop extrusion is accompanied by changes in DNA twist consistent with the motor following the helical pitch of the polynucleotide track. LlaGI is therefore an example of a polypeptide that is a completely self-contained, multi-functional molecular machine.
为了切割 DNA，单个多肽限制修饰酶 LlaGI 必须在一对间接重复的识别位点之间进行通信。我们证明这种通信是通过一维途径发生的，即特定识别序列 5'-CTnGAyG-3'（其中 n 是 A、G、C 或 T，y 是 C 或 T）右侧的单向 dsDNA 环向右平移。数千个碱基对的运动由解旋酶结构域催化，每对碱基需要水解 1.5-2 个 ATP。DNA 环的挤出伴随着 DNA 扭转的变化，与马达沿着多核苷酸轨道的螺旋螺距一致。因此，LlaGI 是一种完全自给自足的多功能分子机器的多肽的例子。
