single-molecule analysis reveals the kinetics and physiological relevance of mutl-ssdna binding单分子的动力学和生理相关性分析显示mutl-ssdna绑定.pdf

Single-Molecule Analysis Reveals the Kinetics and Physiological Relevance of MutL-ssDNA Binding 1 1 1 2,3 4 1,5 Jonghyun Park , Yongmoon Jeon , Daekil In , Richard Fishel *, Changill Ban *, Jong-Bong Lee * 1 Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk, Republic of Korea, 2 Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Medical Center, Columbus, Ohio, United States of America, 3 Physics Department, The Ohio State University, Columbus, Ohio, United States of America, 4 Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk, Republic of Korea, 5 School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk, Republic of Korea Abstract DNA binding by MutL homologs (MLH/PMS) during mismatch repair (MMR) has been considered based on biochemical and genetic studies. Bulk studies with MutL and its yeast homologs Mlh1-Pms1 have suggested an integral role for a single- ¨ stranded DNA (ssDNA) binding activity during MMR. We have developed single-molecule Forster resonance energy transfer (smFRET) and a single-molecule DNA flow-extension assays to examine MutL interaction with ssDNA in real time. The smFRET assay allowed us to observe MutL-ssDNA association and dissociation. We determined that MutL-ssDNA binding required ATP and was the greatest at ionic strength below 25 mM (KD = 29 nM) while it dramatically decreases above 100 mM (KD .2 mM). Single-molecule