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[00:03.60] So, what exactly is a tailspike protein?

[00:07.92] Let's take the Salmonella phage P22 as an example.

[00:12.25] Its tailspike protein was the first one studied in detail.

[00:20.16] This protein, composed of 666 amino acids, is an endo-rhamnosidase and forms a homotrimer.

[00:30.81] It has three domains: a connecting N-terminal domain, a right-handed β-helix domain for polysaccharide recognition, and trimerization domains at the C-terminal.

[00:41.97] Interestingly, swapping the β-helix and trimerization domains between tailspike proteins can change the phage's host range, indicating their their role in receptor specificity.

[00:47.47] As you can see in the picture, tailspike proteins are located in the phage tail.

[00:54.39] At the tail vertex of the virion, six tailspikes attach to a central six-fold-symmetric tailhub.

[01:01.19] Tailspike proteins recognize, attach to, and cleave bacterial cell surface polysaccharides.

[01:08.48] This cleavage then triggers subsequent infection steps, such as viral DNA injection or membrane fusion.

[01:18.13] By acting as receptor binding proteins, tailspike proteins ensure the precise recognition and attachment of the phage to its target bacteria.

[01:23.74] This process plays a crucial role in determining the host specificity of the phage.

[01:29.86] Tailspike proteins can be classified as either Glycoside Hydrolases or Polysaccharide Lyases.

[01:37.86] For example, the tailspike protein from the P22 phage exhibits endo-rhamnosidase activity.

[01:43.42] It cleaves the glycosidic bond of the rhamnose group and belongs to the GH90 family.

[01:50.96] Another example is the tailspike protein from bacteriophage LKA1, which infects Pseudomonas aeruginosa.

[01:57.69] This protein specifically cleaves the trisaccharide repeat of the O5 O-specific antigen and acts as a lyase.

[02:03.60] Tailspike proteins have garnered significant interest for various applications.

[02:09.47] Phage therapy is considered a valuable tool in combating antibiotic resistance.

[02:17.44] Tailspike proteins can help us predict the host specificity of phages, enabling us to narrow down phage selection.

[02:23.50] We can also engineer phages with tailored tailspike proteins for more effective phage therapy.

[02:33.98] Additionally, due to their depolymerase and receptor binding activities, tailspike proteins have been utilized as antimicrobials and in pathogen detection assays.

[02:38.50] Tailspike proteins could be valuable tools for glycoscience.

[02:49.08] With their enzymatic activity resembling restriction enzymes that break down DNA, they can break down polysaccharides into smaller fragments that are easier to study.

[02:59.45] Therefore, there is a great deal of interest in finding more tailspike proteins to learn about their functioning and how they specifically interact with different types of glycans.

[03:06.11] However, identifying tailspike proteins can be quite challenging, especially on a large scale.

[03:14.22] These proteins are parts of phages that undergo rapid evolution and target the highly diverse surface glycans of bacteria.

[03:25.19] As a result, there is considerable sequence divergence among tailspike proteins, making conventional search methods like BLAST and HHpred less effective for their identification.

[03:30.71] Here, we have the structures of various tailspike proteins from the PDB.

[03:39.02] Despite their diverse sequences at the level, they all share a conserved structure characterized by the distinctive right-handed beta-helix domain.

[03:45.67] We leveraged the conserved structure of these proteins and developed a tool named SpikeHunter to identify them.

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