Homologous recombination is a DNA repair technique in which nucleoprotein RAD51 facilitates strand exchange between the broken double-stranded DNA and a homologous strand. RAD51, with assistance from mediators, forms nucleoprotein filaments on single-stranded DNA overhangs produced after a double-stranded break. Mutations in the RAD51 interface can have negative effects on the stability of the nucleoprotein filament. Using FRET and mass photometry this study examines the effect of a mutation in the F86E residue on essential RAD51 functions.