Required for entry into the host cell through presentation or delivery of SipC at the host cell plasma membrane. Along with SipC, is necessary for the transfer of other effector proteins into the host cell. Induces macrophage apoptosis either by binding and activating the proapoptotic enzyme caspase-1 (caspase-1 dependent), resulting in the release of interleukin-1 beta active form, or by disrupting mitochondria and inducing autophagy (caspase-1 independent). The former is dependent of its membrane-fusion activity. The SipBC complex, in association with its chaperone SicA, is regulated by binding of InvE (By similarity). Homotrimer. Secreted via the type III secretion system 1 (SPI-1 TTSS) and inserted into the host cell plasma membrane. SipB membrane integration requires both hydrophobic domains and the helical C-terminal region. Belongs to the invasin protein B family.