Crystal structure of type VI effector Tse1 from Pseudomonas aeruginosa

Abstract

Edited by Renee Tsolis a b s t r a c tThe type VI secretion systems (T6SS) have emerging roles in interspecies competition. In order to have an advantage in defense against other organisms, this system in Pseudomonas aeruginosa delivers a peptidoglycan amidase (Tse1) to the periplasmic space of a competitor. An immune protein (Tsi1) is also produced by the bacterium to protect itself from damage caused by Tse1. Tsi1 directly interacts with Tse1. We report that the crystal structure of Tse1 displays a common CHAP protein fold. Strikingly, our structures showed that the third residue in the catalytic triad may be novel as this residue type has not been observed previously.

Structure of the Type VI Effector-Immunity Complex (Tae4-Tai4) Provides Novel Insights into the Inhibition Mechanism of the Effector by Its Immunity Protein*

“…Note that Tae4 is located in the periplasmic space providing an oxidizing environment favorable for the formation of the disulfide bridge. As reported previously, the disulfide bond is observed in Tae1 and provides structural stability (7,10). This disulfide bridge is also found in the Tae4-Tai4 complex.…”

“…The Dali server was used to find the structural neighbors to Tae4 (29). There are two CHAP (cysteine, histidine-dependent amidohydrolases/peptidase) family functional proteins with Z-scores greater than 5, including endopeptidase YkfC from Bacillus cereus (PDB ID code 3H41) (30) and bacteriolytic effector Tae1 (Tse1) from P. aeruginosa (PDB ID code 4F0V) (10). Despite the low sequence similarity, superpositions of Tae4 with the two proteins give r.m.s.d.…”

“…Recombinant proteins were purified as described previously (10). Briefly, the protein expression was induced by adding 0.5 mM isopropyl ␤-D-thiogalactopyranoside at 289 K. The supernatant was loaded onto a 2-ml Ni-nitrilotriacetic acid resin column (GE Healthcare) and eluted with buffer B (25 mM TrisHCl, pH 8.0, 50 mM NaCl, 5% v/v glycerol) containing 250 mM imidazole.…”

“…Our group and others have solved the crystal structures Tae1 and its complex with Tai1 from P. aeruginosa and revealed the structural mechanisms for the inhibition of Tae1 by Tai1 (7)(8)(9)(10). But so far the structure of Tae4 has not been reported.…”

Structural Insights on the Bacteriolytic and Self-protection Mechanism of Muramidase Effector Tse3 in Pseudomonas aeruginosa

“…Both belong to the cysteine peptidase NlpC/ P60 superfamily (16,18,19,21,22), whereas Tse3 contains an ARM/HEAT-like N-terminal domain and a goose-type lysozyme-like C-terminal catalytic domain (Fig. 1A).…”