Fig. 2: The Bacillus inaquosorum TLP structure is homologous to mammalian Teneurin.
From: Ancestral neuronal receptors are bacterial accessory toxins
a Schematic representation of BiTLP domain organisation. Bacterial Immunoglobulin-like domain, BIG (yellow), TTR (dark blue), TIP (aqua blue), FN-plug (forest green), NHL (lime green), YD-shell (orange), CTD (light grey). Putative autoproteolytic cleavage sites are indicated with scissors. The RHS motif is highlighted (yellow letters). The construct used for structural studies (residues 398-2237) is outlined by a grey line. b the cryogenic electron microscopy density map is colored according to the domain it represents, FN-plug (forest green), NHL (lime green), YD-shell (orange), CTD (light grey). c Cartoon representation of the BiTLP model, colored according to (b). Black arrows indicate autoproteolytic cleavage sites. The N-terminal chain end is indicated with a blue arrow. d Zoomed views. Top: the cleavage site within the RHS motif, containing the aspartyl protease catalytic residues D2116 and D2140 and the conserved R2103. Bottom: the cleavage site in the FN-plug domain is highlighted by a black arrow. The residues flanking the cleavage site are indicated (E722 and S724). C719 forms a covalent bond with C2216, linking the N-terminal fragment to the C-terminal fragment. e Cartoon representation of chicken Teneurin 2 (PDB id:6FB324), colored in analogy to the BiTLP domain organisation in (b). The C-terminal region downstream of the YD-shell is shown as a surface representation (light grey). f As (e), but showing BiTLP, in the same cartoon/surface representation and equivalent colour scheme. g Overlay of the C-terminal regions of chicken Teneurin 2 (dark grey) and BiTLP (light grey). h Propidium accumulation in E.coli cells expressing the BiTLP CTD with or without an N-terminal secretion signal peptide were imaged using HiLo microscopy. Scale bar =5um. i Quantification of propidium accumulation in E.coli cells, presented as box plot showing the median (central line), the first to the third quartile (box limit) and the minima and maxima (whisker). Data represents an average of 3 independent repeats (n = 3). Two-way ANOVA with Tukey’s multiple comparisons test was performed; adjusted p-value ****<0.0001, ns=non-significant.
