ABSTRACT
An essential mechanism for repairing DNA double-strand breaks is homologous recombination (HR). One of its core catalysts is human RAD51 (hRAD51), which assembles as a helical nucleoprotein filament on single-stranded DNA, promoting DNA-strand exchange. Here, we study the interaction of hRAD51 with single-stranded DNA using a single-molecule approach. We show that ATP-bound hRAD51 filaments can exist in two different states with different contour lengths and with a free-energy difference of ~4 kBT per hRAD51 monomer. Upon ATP hydrolysis, the filaments convert into a disassembly-competent ADP-bound configuration. In agreement with the single-molecule analysis, we demonstrate the presence of two distinct protomer interfaces in the crystal structure of a hRAD51-ATP filament, providing a structural basis for the two conformational states of the filament. Together, our findings provide evidence that hRAD51-ATP filaments can exist in two interconvertible conformational states, which might be functionally relevant for DNA homology recognition and strand exchange.
Subject(s)
Adenosine Triphosphate/metabolism , DNA, Single-Stranded/metabolism , DNA-Binding Proteins/metabolism , Homologous Recombination/physiology , Rad51 Recombinase/metabolism , Adenosine Triphosphate/chemistry , Crystallography, X-Ray , DNA/metabolism , DNA Breaks, Double-Stranded , DNA Repair/physiology , DNA Replication/physiology , DNA, Single-Stranded/chemistry , Models, Molecular , Molecular Conformation , Nucleoproteins/metabolism , Rad51 Recombinase/chemistryABSTRACT
A study of kinesin-1 has shed new light on how motor proteins are able to move along microtubules inside cells.
