Bactaegion does not duplicate any scientific data. Everything comes from public databases.
The system that changes the backbone of its own DNA so it isn't mistaken for the enemy.
Ssp family. It modifies the bacterial DNA backbone (phosphorothioate, a sulfur atom replacing a non-bridging oxygen) to distinguish self from non-self. Discovered in Streptomyces lividans. Expanded in 2024 (Picton et al., mBio).
Imagine you want to tell your own mail apart from spam. One bacterium found a radical solution: chemically modify its entire DNA with phosphorothioate (PT) groups — a sulfur atom replacing an oxygen in the phosphate bond. Its own defense proteins (SspB, SspC, SspD) lay down this signature; and SspE, the GTPase effector carrying an HNH nuclease, cleaves any DNA that does NOT bear this signature. So incoming phage DNA, unmodified, gets chopped up. It's immunity through epigenetics — the bacterium marks "self" in chemical terms, and the effector targets "non-self" by default. Remarkable algorithmic elegance.
No direct human ortholog, but the "recognize-hydrolyze-activate" paradigm transfers to other allosterically regulated GTPases (dynamins, septins). It is also a beautiful synthetic biology tool: one can engineer bacteria with customized PT-dependent immunity.
The 2026 cryo-EM (Zhou et al.) showed that SspE forms an asymmetric tetramer in which recognition of the 5'-CPSCA-3' motif by a Y63 residue triggers a cascade: GTP hydrolysis (by R133), allosteric rearrangement, and release of the C-terminal HNH domain for cleavage. Three mutations (Y63A, R133A, N724A) each completely abolish defense. Three breakpoints, therefore three potential inhibition sites.
