期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：32
页码：11611-11616
DOI：10.1073/pnas.0404369101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Branch migration of Holliday junctions is an important step of genetic recombination and DNA repair. In Escherichia coli, this process is driven by the RuvAB complex acting as a molecular motor. Using magnetic tweezers, we studied the RuvAB-directed migration of individual Holliday junctions formed between two {approx}6-kb DNA molecules of identical sequence, and we measured the migration rate at 37{degrees}C and 1 mM ATP. We directly demonstrate that RuvAB is a highly processive DNA motor protein that is able to drive continuous and unidirectional branch migration of Holliday junctions at a well defined average speed over several kilobases through homologous sequences. We observed directional inversions of the migration at the DNA molecule boundaries leading to forth-and-back migration of the branch point and allowing us to measure the migration rate in the presence of negative or positive loads. The average migration rate at zero load was found to be {approx}43 bp/sec. Furthermore, the load dependence of the migration rate is small, within the force range of -3.4 pN (hindering force) to +3.4 pN (assisting force).
