AbiE is a family of an anti-phage defense systems. They act through a Toxin-Antitoxin mechanism, and are comprised of a pair of genes, with one gene being toxic while the other confers immunity to this toxicity.
It is classified as an Abortive infection system.
## Description
AbiE was discovered in 1995 on a Lactococcal plasmid :ref{doi=10.1128/aem.61.12.4321-4328.1995} together with AbiF a homolog of [AbiD](/defense-systems/abid)](/defense-systems/abid).
AbiE is one of the so-called "Abi" systems for "Abortive infection" discovered in the 90's in research related to the dairy industry :ref{doi=10.1016/j.mib.2005.06.006}. AbiE is classified as abortive infection in :ref{doi=10.1016/j.mib.2023.102312}.
AbiE is composed of two proteins: AbiEi and AbiEii. AbiEii is annotated as a nucleotidyltransferase.
## Molecular mechanism
AbiE systems are encoded by two mandatory genes, abiEi and abiEii (1,2). The latter encodes for AbiEii, a GTP-binding nucleotidyltransferase (NTase) which expression induce a reversible growth arrest. On the other hand, abiEi encodes for a AbiEi a transcriptional autorepressor that binds to the promoter of the abiE operon.
AbiE is a family of anti-phage defense systems. They act through a Toxin-Antitoxin mechanism, and are comprised of a pair of genes, with one gene being toxic while the other confers immunity to this toxicity :ref{doi=10.1093/nar/gkt1419}.
AbiEii is a GTP-binding nucleotidyltransferase (NTase) whose expression induces a reversible growth arrest :ref{doi=10.1093/nar/gkt1419}. On the other hand, AbiEi is a transcriptional autorepressor that binds to the promoter of the abiE operon.
Based on these mechanisms, AbiE systems are classified as Type IV Toxin-Antitoxin systems, where the antitoxin and toxin are both proteins that do not directly interact with each other :ref{doi=10.1093/nar/gkt1419}.
Based on this mechanisms, AbiE systems are classified as Type IV Toxin-Antitoxin system, where the antitoxin and toxin are both proteins that do not directly interact with each other.
