Structure of the T6SS lipoprotein TssJ1 from Pseudomonas aeruginosa

Abstract

The type VI secretion system of Pseudomonas aeruginosa has been shown to be responsible for the translocation of bacteriolytic effectors into competing bacteria. A mechanistic understanding of this widely distributed secretion system is developing and structural studies of its components are ongoing. Two representative structures of one highly conserved component, TssJ, from Escherichia coli and Serratia marcescens have been published. Here, the X-ray crystal structure of TssJ1 from P. aeruginosa is presented at 1.4 Å resolution. The overall structure is conserved among the three proteins. This finding suggests that the homologues function in a similar manner and bolsters the understanding of the structure of this family of proteins.

Keywords: Pseudomonas aeruginosa; T6SS; TssJ1; lipoproteins.

Figure 1

(a) The crystal of PaTssJ1. The scale bar represents 200 µm. (b) The crystal structure of PaTssJ1 represented by its secondary structure. The strands of PaTssJ1 are numbered sequentially, as are the helices. The structure is colour-ramped from the N-terminus (blue) to the C-terminus (red). (c) Iodide coordination by PaTssJ1. The protein is shown as green sticks, a representative I atom is shown as a purple sphere and the electron-density map is shown as a blue mesh. The 2F _o − F _c map is displayed at 2.0σ (1.01 e⁻ Å⁻³).

Figure 2

(a) Structural alignment of TssJ homologues. The structural alignment was generated using SALIGN, which takes into account both sequence and structural identity (Braberg et al., 2012 ▶). The two homologues of PaTssJ1 shown are the two TssJ homologues for which structures have been solved. The secondary structure from the crystal structure of PaTssJ1 is shown above the sequence alignment. (b) Structural comparison of TssJ homologues. The side-by-side comparison of the three homologous structures highlights their similarities. The insertion of a helix between β6 and β7 in SmTssJ is the largest additional feature that is present among the three.