[May 22, 2014] 이종봉 교수 연구실 - Loading Dynamics of a Sliding DNA clamp

DNA 복제 단백질인 β clamp가 DNA에 loading되는 과정을 single-molecule Förster Resonance Energy Transfer (FRET)와 single-molecule polarization 기술을 이용하여 실시간으로 관측하였다. 본 연구결과는 Angewandte Chemie에 게제되었으며 (2014년 5월 22일), 이종봉 교수 실험실의 조원기 박사(제 1저자)와 김대형 학생(공저자)이 실험을 수행하였다. 

Sliding DNA clamps are loaded at a ss/dsDNA junction by a clamp loader that depends on ATP binding for clamp opening. Sequential ATP hydrolysis results in closure of the clamp so that it completely encircles and diffuses on dsDNA. We followed events during loading of an E. coli β clamp in real time by using single-molecule FRET (smFRET). Three successive FRET states were retained for 0.3 s, 0.7 s, and 9 min: Hydrolysis of the first ATP molecule by the γ clamp loader resulted in closure of the clamp in 0.3 s, and after 0.7 s in the closed conformation, the clamp was released to diffuse on the dsDNA for at least 9 min. An additional single-molecule polarization study revealed that the interfacial domain of the clamp rotated in plane by approximately 8° during clamp closure. The single-molecule polarization and FRET studies thus revealed the real-time dynamics of the ATP-hydrolysis-dependent 3D conformational change of the β clamp during loading at a ss/dsDNA junction.