title: Structural insight into how Pseudomonas aeruginosa peptidoglycanhydrolase Tse1 and its immunity protein Tsi1 function.
abstract: Tse1 (Tse is type VI secretion exported), an effector protein produced by Pseudomonas aeruginosa, is an amidase that hydrolyses the γ-D-glutamyl-DAP (γ-D-glutamyl-L-meso-diaminopimelic acid) linkage of the peptide bridge of peptidoglycan. P. aeruginosa injects Tse1 into the periplasm of recipient cells, degrading their peptidoglycan, thereby helping itself to compete with other bacteria. Meanwhile, to protect itself from injury by Tse1, P. aeruginosa expresses the cognate immunity protein Tsi1 (Tsi is type VI secretion immunity) in its own periplasm to inactivate Tse1. In the present paper, we report the crystal structures of Tse1 and the Tse1-(6-148)-Tsi1-(20-end) complex at 1.4 Å and 1.6 Å (1 Å=0.1 nm) resolutions respectively. The Tse1 structure adopts a classical papain-like α+β fold. A cysteine-histidine catalytic diad is identified in the reaction centre of Tse1 by structural comparison and mutagenesis studies. Tsi1 binds Tse1 tightly. The HI loop (middle finger tip) from Tsi1 inserts into the large pocket of the Y-shaped groove on the surface of Tse1, and CD, EF, JK and LM loops (thumb, index finger, ring finger and little finger tips) interact with Tse1, thus blocking the binding of enzyme to peptidoglycan. The catalytic and inhibition mechanisms provide new insights into how P. aeruginosa competes with others and protects itself.
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China.
authors.forename: Guijun
authors.initials: G
authors.lastname: Shang
authors.forename: Xiuhua
authors.initials: X
authors.lastname: Liu
authors.forename: Defen
authors.initials: D
authors.lastname: Lu
authors.forename: Junbing
authors.initials: J
authors.lastname: Zhang
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.forename: Chunyuan
authors.initials: C
authors.lastname: Zhu
authors.forename: Shiheng
authors.initials: S
authors.lastname: Liu
authors.forename: Qian
authors.initials: Q
authors.lastname: Yu
authors.forename: Yanyu
authors.initials: Y
authors.lastname: Zhao
authors.forename: Heqiao
authors.initials: H
authors.lastname: Zhang
authors.forename: Junqiang
authors.initials: J
authors.lastname: Hu
authors.forename: Huaixing
authors.initials: H
authors.lastname: Cang
authors.forename: Sujuan
authors.initials: S
authors.lastname: Xu
authors.forename: Lichuan
authors.initials: L
authors.lastname: Gu
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D046912:Multiprotein Complexes; D011994:Recombinant Proteins; D009238:N-Acetylmuramoyl-L-alanine Amidase