Actin-binding protein that interferes with host cell actin cytoskeleton. Nucleates actin polymerization and condensates actin filaments into cables (bundling). SipA potenciates SipC activity and both are required for an efficient bacterial internalization by the host cell. Secreted via the type III secretion system 1 (SPI-1 TTSS) and inserted into the host cell plasma membrane. Belongs to the invasin protein C family.