Fig. 6: Structure of the BRCA2MBD–MEILB2–BRME1MBD 2:4:4 ternary complex.
From: MEILB2-BRME1 forms a V-shaped DNA clamp upon BRCA2-binding in meiotic recombination
a SEC-MALS analysis of MEILB2–BRME1MBD (blue) and the BRCA2MBD–MEILB2–BRME1MBD ternary complex (red), showing differential refractive index (dRI; solid lines) profiles with fitted molecular weights (Mw; dashed lines) across elution peaks. MEILB2–BRME1MBD forms a 76 kDa 2:2 complex (theoretical Mw—82 kDa), and BRCA2MBD–MEILB2–BRME1MBD forms a 161 kDa 2:4:4 complex (theoretical Mw—176 kDa). SDS–PAGE of elution fractions are shown in Supplementary Fig. 8a, b. b Model of the BRCA2MBD–MEILB2–BRME1MBD 2:4:4 complex generated by docking two MEILB2–BRME1MBD 2:2 complex models (shown in Fig. 4a) onto the BRCA2MBD–MEILB2 ARM domain 2:4 complex crystal structure PDB accession 7LDG43. The model predicts that the DNA-binding β-caps of the two constituent MEILB2α–BRME1MBD core complexes are separated by 25 nm. Modelling details are shown in Supplementary Fig. 9. c Cryo-EM reference-free 2D class averages of the BRCA2MBD–MEILB2–BRME1MBD 2:4:4 complex (21,175 particles). Scale bars, 10 nm. d Cryo-EM ab initio 3D model of the BRCA2MBD–MEILB2–BRME1MBD 2:4:4 complex (13,027 particles; GSFSC = 13 Å), indicating an angle of ~100° between limbs and a 25 nm distance between β-caps at the N-terminal ends of its limbs. e SEC-SAXS data in which the BRCA2MBD–MEILB2–BRME1MBD scattering curve is overlaid with the theoretical scattering curve of the 2:4:4 modelled structure (red; shown in (b)), with a χ2 value of 1.36. Residuals are shown (inset). Guinier analysis and real-space P(r) distribution are shown in Supplementary Fig. 10. f Schematic of BRCA2MBD–MEILB2–BRME1MBD complex formation, in which BRCA2-binding induces dimerisation of two MEILB2–BRME1MBD 2:2 complexes into a V-shaped 2:4:4 complex.
