Visualizing a Complete Siphoviridae Member by Single-Particle Electron Microscopy: the Structure of Lactococcal Phage TP901-1

Abstract

c Tailed phages are genome delivery machines exhibiting unequaled efficiency acquired over more than 3 billion years of evolution. Siphophages from the P335 and 936 families infect the Gram-positive bacterium Lactococcus lactis using receptor-binding proteins anchored to the host adsorption apparatus (baseplate). Crystallographic and electron microscopy (EM) studies have shed light on the distinct adsorption strategies used by phages of these two families, suggesting that they might also rely on different infection mechanisms. Here, we report electron microscopy reconstructions of the whole phage TP901-1 (P335 species) and propose a composite EM model of this gigantic molecular machine. Our results suggest conservation of structural proteins among tailed phages and add to the growing body of evidence pointing to a common evolutionary origin for these virions. Finally, we propose that host adsorption apparatus architectures have evolved in correlation with the nature of the receptors used during infection.

The First Structure of a Mycobacteriophage, the Mycobacterium abscessus subsp. bolletii Phage Araucaria

“…8). The capsid and head-to-tail connector complex exhibit structures and overall dimensions very similar to those of other Siphoviridae, especially phages SPP1 (38,45) and TP901-1 (14). The only difference between Araucaria and TP901-1 is the size of the stopper, much larger in the latter case.…”

“…The portal, a dodecameric protein, discloses a conserved fold in tailed phages and herpesviruses (14,36). It is involved in DNA packaging during assembly and in DNA release when phage infection occurs.…”

“…6B and C). The tail tube displays a 40-Å-wide central channel between the connector and the baseplate, which forms the DNA ejection passage (14,45) (Fig. 6C).…”

“…To date, no other EM structure of any mycobacteriophage has been described. Due to the highly flexible nature of Siphoviridae tails, which limits the structural characterization, we used a methodology specially implemented to characterize their tail (14). Based on our EM reconstructions and bioinformatics analysis, we could achieve a pseudoatomic model for some parts of this siphoviridal virion and reveal the striking features of Araucaria's tail and host adsorption device (HAD).…”

Molecular architecture of tailed double-stranded DNA phages

“…128,129 The tail tip complex has different size and morphology in different phages. Phages which use protein receptors for cell binding usually have conical tail tips (e.g., SPP1 130 and λ), whereas phages, using polysaccharide receptors usually have elaborate baseplates at the distal end of the tail (e.g., lactococcal phages TP901-1 6,131 and p2 132,133 ). Furthermore phages usually have side tail fibers or spikes, attached to the periphery of the tail tip complex, as well as a central tail spike.…”