Structural flexibility of the periplasmic protein, FlgA, regulates flagellar P-ring assembly in Salmonella enterica

Abstract

A periplasmic flagellar chaperone protein, FlgA, is required for P-ring assembly in bacterial flagella of taxa such as Salmonella enterica or Escherichia coli. The mechanism of chaperone-mediated P-ring formation is poorly understood. Here we present the open and closed crystal structures of FlgA from Salmonella enterica serovar Typhimurium, grown under different crystallization conditions. An intramolecular disulfide cross-linked form of FlgA caused a dominant negative effect on motility of the wild-type strain. Pull-down experiments support a specific protein-protein interaction between FlgI, the P-ring component protein, and the C-terminal domain of FlgA. Surface plasmon resonance and limited-proteolysis indicate that flexibility of the domain is reduced in the covalently closed form. These results show that the structural flexibility of the C-terminal domain of FlgA, which is related to the structural difference between the two crystal forms, is intrinsically associated with its molecular chaperone function in P-ring assembly.

Structure of the molecular bushing of the bacterial flagellar motor

“…The N-terminal signal peptides are cleaved during the translocation across the cell membrane 17 , 18 . FlgI molecules assemble around the distal rod with the help of the FlgA chaperone to form the P ring 19 , 20 . The P ring tightly associates with the PG layer, allowing the LP ring to act as a molecular bushing.…”

Adaptation strategies of Pseudomonas protegens SN15‐2 to hyperosmotic growth environment

“…This may have occurred because although the flagellum is normally assembled or even significantly up‐regulated, this organelle does not enhance the motility of the bacteria. In most Gram‐negative bacteria, flagellation of cells cannot occur in the absence of FlgA (Matsunami et al ), which is required for morphogenesis and elongation of the flagellar filament by facilitating polymerization of the flagellin monomers at the tip of the growing filament. It could be hypothesized that owing to the adequate nutrition of the culture and homogeneous stressful environment, the P. protegens in the stable stage did not roll and move to seek nutrition or avoid pressure because of the stressful environment.…”

Mutations involved in the emergence of Yersinia ruckeri biotype 2 in France

“…Finally, the last mutation observed in the French BT2 strains was within the flgA gene. FlgA is a periplasmic flagellar chaperone protein required for P ring formation in bacterial flagella of Salmonella enterica and E. coli (Matsunami, Yoon, Meshcheryakov, Namba, & Samatey, ; Nambu & Kutsukake, ). The flgA mutant of Campylobacter jejuni was completely devoid of flagella and was non‐motile (Kim, Park, & Kim, ).…”

“…coli (Matsunami, Yoon, Meshcheryakov, Namba, & Samatey, 2006;Nambu & Kutsukake, 2000). The flgA mutant of Campylobacter jejuni was completely devoid of flagella and was non-motile (Kim, Park, & Kim, 2015).…”