This is the N-terminal domain of the T6S-associated protein, TagF. A post-translational repressor of the hemolysin co-regulated secretion island I (HSI-I)-encoded type VI secretion system (H1-T6SS) found in Pseudomonas aeruginosa. The type VI secretion system (T6SS) is found broadly among the Proteobacteria and is implicated in diverse processes including host-cell interactions, biofilm formation and gene regulation. Furthermore, studies indicate that the T6SS plays a critical role in interbacterial interactions. TagF has been shown to regulate the activity of the H1-T6SS in a manner that does not require phosphorylated-Fha1, PpkA, or other Tag proteins. Additionally TagF is found to associate as a homodimer with nearly identical monomers composed of alpha and beta elements assembled as a three-layer sandwich (alpha-beta-alpha) [1].

1: Separate inputs modulate phosphorylation-dependent and -independent type VI secretion activation. Silverman JM, Austin LS, Hsu F, Hicks KG, Hood RD, Mougous JD; Mol Microbiol. 2011;82:1277-1290. PMID:22017253