Bacterial virus anti-defence systems · sequence & structure resource

Encyclopaedia of Bacterial Virus Anti-Defence Systems


Protein: LockinA

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Overview

Mode of Action (MoA) bind and sequester the TIR-produced signaling molecules 3′cADPR and His-ADPR
Evidence Lockin was identified as a broad-spectrum anti-Thoeris sponge family by infectivity assays showing that multiple Lockin proteins restored phage SBSphiJ propagation in cells expressing type I and/or type II Thoeris systems. Infected cells co-expressing Lockin and ThsB failed to accumulate 3′cADPR, as shown by NADase-based assays. Biochemical validation included size-exclusion chromatography (ECO_0000325) and HPLC (ECO_0001272) confirming direct binding and reversible sequestration of 3′cADPR by Lockin. Crystallography of LockinA with 3′cADPR revealed a homo-hexameric complex (ECO_0001171) with six deep inter-protomer pockets sequestering the signaling molecule. Mutations in pocket-coordinating residues K45 and K48 impaired anti-defense activity, confirming their role in nucleotide binding.
MoA Category degrades or sequesters molecules utilised by host defence systems
Subtype(s) of the defence system(s) inhibited by the protein Defence Subtype Bacillus cereus MSX-D12 type I Thoeris and Bacillus amyloliquefaciens Y2 type II Thoeris
Relevant publication(s) DOI 10.1101/2025.07.12.664507
Other components of the anti-defence system Multicomponent System -
Known structure in PDB PDB ID -
Genome(s) encoding the protein Protein Source Metagenomics data (IMG_VR ID: IMGVR_UViG_3300014204_000177)
Defence system(s) inhibited by the protein Defences Thoeris

3D structure

AlphaFold 3 model.

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Feature viewer - predicted secondary structure

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Pfam annotations

No Pfam domains found

Sequence Viewer

Amino acid position: -

MKEKDLGITEVRGAKANITDLVVYGNGDTFALLCKASSQEQGWMKSTKVCNVYGGCIVQVTTQQRNPDGSYALAEALTFVPNNHIDTSGNTRFIGKI