Design, synthesis and interaction of BRC4 analogous peptides with RAD51(241–260)

Breast cancer susceptibility gene 2 (BRCA2) is an important tumor suppressor, which is participated in repair of damaged DNA by its highly conserved BRC repeat motifs regulating RAD51 protein homologous recombination and thereby preventing cell carcinogenesis. In this study, the BRCA2(1524–1548)–RAD51(241–260) complex structure was obtained based on PDB bank data 1N0W, which provided the basis for site-specific mutation of BRCA2(1524–1548). The BRC4 and BRC4 analogous peptides were synthesized, and the interaction between BRC peptide and RAD51(241–260) was studied by fluorescence spectroscopy, circular dichroism spectroscopy and microscale thermophoresis (MST). The results of circular dichroism showed that the changes in secondary structures of RAD51(241–260) occurred after adding BRC4 analogous peptides, and the α-helix content increased significantly. Fluorescence spectral data demonstrated that the model of BRC peptide binding to RAD51(241–260) was static quenching, and the binding constants of BRC4, P1, P2, P4 with RAD51(241–260) were 1.647 × 10−4 L mol−1, 2.532 × 10−4 L mol−1, 3.161 × 10−4 L mol−1, 1.705 × 10−4 L mol−1, respectively. The results of MST indicated that P2 and RAD51(241–260) have better affinity for dissociation constant 44.286 μM. The strongest affinity between P2 and RAD51(241–260) indicated that the mutation of amino acid residue constituting BRC α-helix affects the structure and interaction of BRC peptide and RAD51(241–260).