Abstract
Bacteriophages can play beneficial roles in phage therapy and destruction of food pathogens. Conversely, they play negative roles as they infect bacteria involved in fermentation, resulting in serious industrial losses. Siphoviridae phages possess a long non-contractile tail and use a mechanism of infection whose first step is host recognition and binding. They have evolved adhesion devices at their tails’ distal end, tuned to recognize specific proteinaceous or saccharidic receptors on the host’s surface that span a large spectrum of shapes. In this review, we aimed to identify common patterns beyond this apparent diversity. To this end, we analyzed siphophage tail tips or baseplates, evaluating their known structures, where available, and uncovering patterns with bioinformatics tools when they were not. It was thereby identified that a triad formed by three proteins in complex, i.e., the tape measure protein (TMP), the distal tail protein (Dit), and the tail-associated lysozyme (Tal), is conserved in all phages. This common scaffold may harbor various functional extensions internally while it also serves as a platform for plug-in ancillary or receptor-binding proteins (RBPs). Finally, a group of siphophage baseplates involved in saccharidic receptor recognition exhibits an activation mechanism reminiscent of that observed in Myoviridae.
Highlights
Viruses that infect bacteria, commonly named bacteriophages or phages, play an upmost role in biogeochemistry, biomes, health, and industry
The pb1 C-terminal receptor-binding domain is formed by intertwined β-sheets with a bullet-like shape, which is different from the predicted fold of the lambda long tail fibers (LTFs) C-terminal domains (Figure 4b) [73]
Whereas phages that bind to a host protein have an elongated tail tip, phages binding to cell wall surface polysaccharides possess a bulky distal tail feature named the baseplate
Summary
Commonly named bacteriophages or phages, play an upmost role in biogeochemistry, biomes, health (phage therapy), and industry. Tailed phage (Caudovirales), phages with a tail attached to the capsid and a double-stranded DNA genome, dominate among those found in public databases, e.g., NCBI, with 58% of all phages possessing this morphology [3]. There has been an upsurge of interest in siphophages, especially those infecting Gram-positive bacteria, driven by the public safety and economic relevance of their hosts, which started to slowly dissect their infection mechanisms [10,11,12,13,14,15]. We pursue by inserting in this frame the different peripheral proteins such as the receptor-binding proteins (RBPs), the tail fibers, and other ancillary proteins
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