New helicase mechanism to regulate recombination
Using Single-Molecule FRET techniques, CPLC student, Jeehae Park, found that PcrA can processively pull the ssDNA from the duplex junction, and thereby effectively dismantle filaments formed from RecA, the mediator of recombination. Molecular details of this activity were further investigated via an alternating excitation technique developed by graduate student, Kyungsuk Lee, and the role and the conformation of the subdomains within the protein machinery were identified.
This study has also answered more fundamental questions on how such biological motor proteins work. PcrA is a prototypical DNA motor protein that converts chemical energy of ATP hydrolysis into the mechanical energy of directional movement along the DNA. Our single-molecule approach revealed that molecular heterogeneity exists in the dynamics among the population of molecules, and when this heterogeneity is removed, clear kinetics are revealed; the motor operates in one-nucleotide uniform steps. This information was previously inaccessible and therefore was not measured precisely even with the most advanced biochemical techniques.