Salmonella enterica serovar Paratyphi A flagellin (FliC) (FliC)

Salmonella enterica serovar Paratyphi A flagellin, primarily the FliC protein, is the major structural subunit that polymerizes to form the helical filaments of bacterial flagella, enabling motility on surfaces and within host cell cytosol.[1][2][5][6] In this human-restricted typhoidal serovar, which causes paratyphoid fever, flagellin supports key virulence processes including epithelial cell invasion, macrophage uptake, and evasion of xenophagy through flagella-mediated cytosolic movement, independent of swimming motility in some contexts.[1][2][3][4] Unlike polyphasic serovars like S. Typhimurium, S. Paratyphi A is monophasic due to genomic inactivation of genes like hin, expressing only phase 1 FliC flagellin at lower levels, which correlates with reduced motility but retained invasion capability.[1][2] Absence of FliC uniquely upregulates the flagellar regulon and Salmonella pathogenicity island 1 (SPI-1) in a FliZ-dependent manner, leading to oversecretion of SPI-1 effectors via type III secretion system 1, enhancing invasion without affecting adhesion.[1][2] Flagellin also contributes to host immune recognition as a Toll-like receptor 5 agonist, though no approved drugs directly target it therapeutically.[9] These features distinguish S. Paratyphi A pathogenesis from nontyphoidal Salmonella, underscoring flagellin's regulatory role in systemic infection.[1][2][3]

Other names

phase 1 flagellinFliC flagellin