Direct Evaluation of a Kinetic Model for RecA‐Mediated DNA‐strand exchange: The Importance of Nucleic Acid Dynamics and Entropy During Homologous Genetic Recombination

摘要: The Escherichia coli RecA protein is the prototype of a class proteins that play central roles in genomic repair and recombination all organisms. unresolved mechanistic strategy by which aligns single strand DNA with duplex mediates switch to understanding homologous recombination. We explored mechanism RecA-mediated DNA-strand exchange using oligonucleotide substrates intrinsic fluorophore 6-methylisoxanthopterin. Pre-steady-state spectrofluorometric analysis elucidated earliest transient intermediates formed during delineated facilitates this process. structural features first detectable intermediate energetic characteristics its formation were consistent interactions between few bases single-stranded minor groove locally melted or stretched DNA. Further revealed be an unusual enzyme entropic rather than enthalpic contributions dominate catalytic function, no unambiguously active role for was detected molecular events data best support conclusion likely relies on dynamics.