6p8v

Structural highlights

Function

CAP6_ECOM1 CBASS (cyclic oligonucleotide-based antiphage signaling system) provides immunity against bacteriophage. The CD-NTase protein synthesizes cyclic nucleotides in response to infection; these serve as specific second messenger signals. The signals activate a diverse range of effectors, leading to bacterial cell death and thus abortive phage infection. A type III-C(AAA) CBASS system (PubMed:32839535).^{[1] [2]} Binds and disassembles an active CdnC:Cap7 (Cap7 is also called HORMA) complex, inhibiting the complex's ability to synthesize cyclic nucleotide second messengers (PubMed:31932165). An AAA+-ATPase remodeler, it is thought that in the absence of foreign threat Cap6 (also called Trip13) maintains the Cap7 protein in its open, inactive state. Once activated (presumably by a bacteriophage protein) Cap7 binds to and activates its cognate CD-NTase (CdnC in this bacteria) to synthesize cAAA, a cyclic nucleotide second messenger. cAAA activates the NucC endonuclease which degrades all DNA in the infected cell, causing cell death and abortive phage infection (Probable).^{[3] [4]} Protects E.coli strain JP313 against bacteriophage lambda cI- infection. When the cdnC-cap7-cap6-nucC operon is transformed into a susceptible E.coli strain it confers bacteriophage lambda cI- immunity. Mutations in the sensor (Cap7 also called HORMA) or effector proteins (CdnC, NucC) but not the disassembly protein (Cap6 also called Trip13) no longer confer immunity. The presence of the intact operon leads to culture collapse and cell death, which occurs before the phage has finished its replication cycle, thus protecting non-infected bacteria by aborting the phage infection and preventing its propagation.^[5]

References

1. ↑ Ye Q, Lau RK, Mathews IT, Birkholz EA, Watrous JD, Azimi CS, Pogliano J, Jain M, Corbett KD. HORMA Domain Proteins and a Trip13-like ATPase Regulate Bacterial cGAS-like Enzymes to Mediate Bacteriophage Immunity. Mol Cell. 2019 Dec 31. pii: S1097-2765(19)30922-0. doi:, 10.1016/j.molcel.2019.12.009. PMID:31932165 doi:http://dx.doi.org/10.1016/j.molcel.2019.12.009
2. ↑ Millman A, Melamed S, Amitai G, Sorek R. Diversity and classification of cyclic-oligonucleotide-based anti-phage signalling systems. Nat Microbiol. 2020 Dec;5(12):1608-1615. doi: 10.1038/s41564-020-0777-y. Epub, 2020 Aug 24. PMID:32839535 doi:http://dx.doi.org/10.1038/s41564-020-0777-y
3. ↑ Ye Q, Lau RK, Mathews IT, Birkholz EA, Watrous JD, Azimi CS, Pogliano J, Jain M, Corbett KD. HORMA Domain Proteins and a Trip13-like ATPase Regulate Bacterial cGAS-like Enzymes to Mediate Bacteriophage Immunity. Mol Cell. 2019 Dec 31. pii: S1097-2765(19)30922-0. doi:, 10.1016/j.molcel.2019.12.009. PMID:31932165 doi:http://dx.doi.org/10.1016/j.molcel.2019.12.009
4. ↑ Ye Q, Lau RK, Mathews IT, Birkholz EA, Watrous JD, Azimi CS, Pogliano J, Jain M, Corbett KD. HORMA Domain Proteins and a Trip13-like ATPase Regulate Bacterial cGAS-like Enzymes to Mediate Bacteriophage Immunity. Mol Cell. 2019 Dec 31. pii: S1097-2765(19)30922-0. doi:, 10.1016/j.molcel.2019.12.009. PMID:31932165 doi:http://dx.doi.org/10.1016/j.molcel.2019.12.009
5. ↑ Ye Q, Lau RK, Mathews IT, Birkholz EA, Watrous JD, Azimi CS, Pogliano J, Jain M, Corbett KD. HORMA Domain Proteins and a Trip13-like ATPase Regulate Bacterial cGAS-like Enzymes to Mediate Bacteriophage Immunity. Mol Cell. 2019 Dec 31. pii: S1097-2765(19)30922-0. doi:, 10.1016/j.molcel.2019.12.009. PMID:31932165 doi:http://dx.doi.org/10.1016/j.molcel.2019.12.009
6. ↑ Ye Q, Lau RK, Mathews IT, Birkholz EA, Watrous JD, Azimi CS, Pogliano J, Jain M, Corbett KD. HORMA Domain Proteins and a Trip13-like ATPase Regulate Bacterial cGAS-like Enzymes to Mediate Bacteriophage Immunity. Mol Cell. 2019 Dec 31. pii: S1097-2765(19)30922-0. doi:, 10.1016/j.molcel.2019.12.009. PMID:31932165 doi:http://dx.doi.org/10.1016/j.molcel.2019.12.009