text_1: The tip of the inner tube of the toxic type VI secretion system (T6SS) antibacterial effector in Escherichia coli (E. coli) carries toxic effector proteins.
text_2: Here we report that proteins from the PAAR (proline-alanine-alanine-arginine) repeat superfamily form a sharp conical extension on the VgrG spike, which is further involved in attaching effector domains to the spike. The crystal structures of two PAAR-repeat proteins bound to VgrG-like partners show that these proteins sharpen the tip of the T6SS spike complex.