T6SS-TLE3

Family: T6SS-TLE3

Block: X

Parent Family: No family

Comment

Family of Tle3 phospholipase effector .The type VI lipase effectors Tle1-Tle5 secreted by the bacterial type VI secretion system (T6SS) have been identified as antibacterial effectors that hydrolyze membrane phospholipids. The Tle1-4 display phospholipase A1 and A2 (PLA1) (PLA2) activities. Tle1 belongs to Duf_2235 family (now T6SS-TLE1), TLE2 to Lipase_3, TLE3 to alpha/ beta hydrolase (now T6SS-TLE3) and Tle4 belongs to PGAP1 (Tle5 family, such as Pseudomonas aeruginosa PldA and PldB, are phospholipases D and are not alpha/beta hydrolases). Tle3 phospholipase effector from adherent-invasive Escherichia coli (AIEC) Tle3AIEC possesses phospholipase A1 (PLA1) activity (specific activity (SA) = 7.65 nmole.min-1.mg-1) but no PLA2 activity. The T6SS-TLE3 is decorated by two protruding segments, including a N-terminus loop containing part of the oxyanion hole residues. The long C-terminus contains the catalytic site histidine and in some members is related to the DUF3274 family (most members of this family are not linked to alpha/beta hydrolases). In T6SS, protection against its own toxic effector is ensured in bacteria by the production of immunity proteins that specifically bind and inhibit Tle3. Tli (Type VI lipase immunity) binds tightly to Tle3. There is also a strong interaction between the VgrGAIEC C-terminus adaptor and Tle3AIEC N-terminal loop.