Bidirectional replication from the origin is a fundamental principle of chromosome replication. This process is thought to require the functional coupling of two DNA helicases loaded onto the origin. In Escherichia coli, two DnaB helicases are loaded onto each single-stranded (ss) DNA region of the origin, oriC, through interactions with a complex of the DNA-bending protein IHF and the initiator protein DnaA oligomers (upper panel). The translocation of one DnaB helicase is stalled by the oriC-IHF-DnaA complex, while the other translocates toward a DnaA-free region, expanding ssDNA region. SSB (Single-stranded binding) proteins then bind to the expanded ssDNA, stabilizing it and enhancing DnaB helicase activity. This allows the stalled DnaB helicase to pass through the oriC-IHF-DnaA complex, displacing the bound proteins (lower panel). This mechanism functionally couples the two DNA helicases at the origin region, ensuring bidirectional replication. Akama, Y., Yoshida, R., Ozaki, S., Kawakami, H., and Katayama, T. (2025) SSB promotes DnaB helicase passage through DnaA complexes at the replication origin oriC for bidirectional replication. J. Biochem. 177, 305-316