Fig. 5: ssDNA binding by OB-1 is modulated by a Rpa1 acidic domain.

a Phylogenetic analysis (bottom) reveals a broad distribution of Rpa1-AROD domain homologs across Archaea. Notably, in some members of the Thermoplasmata, the AROD domain is found as a standalone domain rather than fused to Rpa1. Genomes lacking AROD domain are presented in gray. b High-resolution crystal structure of Rpa1 N-terminal domains at 1.8 Å with a focused view on the AROD/OB-1 dimerization interface. c Sedimentation distribution profile of Rpa1-AROD-OB-1 by sedimentation velocity. The theoretical (MWth) and calculated molecular weights (MWcalc) for each complex are given in kDa. d Specific binding of WT (10, 5, 2.5, 1.25, 0.63, 0.31, 0.16 µM; n = 3) and mutant Rpa1 N-terminal domains (1000, 500, 250, 125, 62.5, 31.3, 15.6 nM; n = 3) to immobilized poly-dT35 ssDNA measured by biolayer interferometry (BLI). Steady-state analyses were performed using the average signal measured at the end of the association steps. Data are represented as mean values ± standard deviations (error bars). Source data are provided as a source data file. e Focus on the AROD/OB-1 interface. On top, all AROD’s aspartates and glutamates residues are represented as spheres. On bottom, the electrostatic surface potential of AROD is shown with negative, neutral, and positive charges represented in red, white, and blue. The structure of human Rpa1 OB-A bound to ssDNA (1JMC) was superimposed onto the OB-1 domain.