이종봉 교수 연구실, “Loading Dynamics of a Sliding DNA clamp”

DNA복제 단백질인 β clamp가DNA에loading되는 과정을 single-molecule FörsterResonance Energy Transfer (FRET)와single-molecule polarization기술을 이용하여 실시간으로 관측하였다.본 연구결과는 Angewandte Chemie에 게제되었으며 (2014년5월22일),이종봉 교수 실험실의 조원기 박사(제1저자)와김대형 학생(공저자)이 실험을 수행하였다.

Sliding DNA clamps are loaded at a ss/dsDNAjunction 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. coliβ 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 γclamp 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 dsDNAfor 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/dsDNAjunction.