Ultrafast Redistribution of E. coil SSB along Long Single-Stranded DNA via lntersegment Transfer

作者：Lee Kyung Suk; Marciel Amanda B; Kozlov Alexander G; Schroeder Charles M; Lohman Timothy M; Ha Taekjip^*

来源：Journal of Molecular Biology, 2014, 426(13): 2413-2421.

DOI：10.1016/j.jmb.2014.04.023

• single-stranded DNA
• single-stranded DNA binding protein
• optical tweezer

Single-stranded DNA binding proteins (SSBs) selectively bind single-stranded DNA (ssDNA) and facilitate recruitment of additional proteins and enzymes to their sites of action on DNA. SSB can also locally diffuse on ssDNA, which allows it to quickly reposition itself while remaining bound to ssDNA. In this work, we used a hybrid instrument that combines single-molecule fluorescence and force spectroscopy to directly visualize the movement of Escherichia coil SSB on long polymeric ssDNA. Long ssDNA was synthesized without secondary structure that can hinder quantitative analysis of SSB movement. The apparent diffusion coefficient of E. coil SSB thus determined ranged from 70,000 to 170,000 nt(2)/s, which is at least 600 times higher than that determined from SSB diffusion on short ssDNA oligomers, and is within the range of values reported for protein diffusion on double-stranded DNA. Our work suggests that SSB can also migrate via a long-range intersegment transfer on long ssDNA. The force dependence of SSB movement on ssDNA further supports this interpretation.

• 出版日期2014-6-26