Design, Synthesis and Interaction of BRCA1 Peptide Fragments with RAD51(181–200)

Six breast cancer susceptibility gene 1 (BRCA1) peptide fragments were designed by removing N-terminal amino acid residues of BRCA1(846–871). Peptide fragments BRCA1(846–871), BRCA1(852–871), BRCA1(854–871), BRCA1(856–871), BRCA1(857–871) and BRCA1(861–871) were obtained by Fmoc solid-phase synthesis, purified by reversed-phase high-performance liquid chromatography and characterized by electrospray ionization mass spectrometry. The interaction between BRCA1 fragment peptides and RAD51(181–200) target peptides were investigated using circular dichroism (CD) spectroscopy, fluorescence spectroscopy, and microscale thermophoresis (MST). The results of CD spectroscopy showed that the secondary structures of RAD51(181–200) were altered after the addition of BRCA1 peptide fragments. The fluorescence results proved that all six BRCA1 peptide fragments BRCA1(846–871), BRCA1(852–871), BRCA1(854–871), BRCA1(856–871), BRCA1(857–871) and BRCA1(861–871) could bind to RAD51(181–200) independently, their quenching processes were static, and the binding constant of peptide fragments with RAD51(181–200) were 4.01 × 105 L mol−1, 7.22 × 105 L mol−1, 7.84 × 105 L mol−1, 1.1 × 104 L mol−1, 6.19 × 103 L mol−1, 6.18 × 103 L mol−1. The results of MST displayed that BRCA1(854–871) could combine with RAD51(181–200), and the dissociation constant Kd was 126.44 µM. Compared with other five peptide fragments, the interaction between BRCA1(854–871) and RAD51(181–200) was much stronger.