Major component of the type III secretion needle structure that plays an essential role in translocation of effector toxins into host cells, facilitating the establishment and dissemination of infection. Forms a stable heterotrimeric complex with PscE and PscG in the cytoplasm, blocking it in a monomeric state and preventing its polymerization (PubMed:16115870, PubMed:17470796). Then, forms a polymeric structure at the cell surface (PubMed:16115870). Secreted via type III secretion system (TTSS). The N-terminal part (1-11) is species-specific and essential for export/assembly and the function of needle. Belongs to the MxiH/PrgI/YscF family.