Structure of the host cell recognition and penetration machinery of a Staphylococcus aureus bacteriophage

Abstract

Staphylococcus aureus is a common cause of infections in humans. The emergence of virulent, antibiotic-resistant strains of S. aureus is a significant public health concern. Most virulence and resistance factors in S. aureus are encoded by mobile genetic elements, and transduction by bacteriophages represents the main mechanism for horizontal gene transfer. The baseplate is a specialized structure at the tip of bacteriophage tails that plays key roles in host recognition, cell wall penetration, and DNA ejection. We have used high-resolution cryo-electron microscopy to determine the structure of the S. aureus bacteriophage 80α baseplate at 3.7 Å resolution, allowing atomic models to be built for most of the major tail and baseplate proteins, including two tail fibers, a trimeric receptor binding protein, and part of the tape measure protein. Our structure provides a structural basis for understanding host recognition, cell wall penetration and DNA ejection in viruses infecting Gram-positive bacteria. Comparison to other phages demonstrate the modular design of baseplate proteins, and the adaptations to the host that take place during the evolution of staphylococci and other pathogens.

Revisiting the host adhesion determinants of Streptococcus thermophilus siphophages

“…confirms the presence of large bulbs following a six-mer (C6) symmetry, attached to the baseplate core. The presence of an N-terminal BppU-like domain suggests that this ORF may form a 18-mer ring above the Dit as observed in phages TP901-1 and Tuc2009 (Veesler, et al, 2012;Legrand, et al, 2016) and Staphylococcus aureus phage 80a (Kizziah, et al, 2020). This Dit ring would then project six trimeric linkers to each of which a trimeric RBP is attached (Fig.…”

Architecture of the flexible tail tube of bacteriophage SPP1

“…S7)-all featuring hexameric, helically stacked rings with subunits consisting of a β-sandwich-type fold and one parallel α-helix. Loop 40-59 is present at the interface between subunits in all described Siphoviridae phages 7,8,10,11 , Siphoviridae-like systems 12 and T4 phage 4 , suggesting that it is a conserved structural element across both Siphoviridae and Myoviridae families as it was also proposed to play a regulatory role during tail polymerization. The mentioned C-arm is only present in SPP1 and 80α 10 (even if not completely resolved).…”

“…Structural information was limited to pseudo-atomic models, which were generated for SPP1 6 based on solution nuclear magnetic resonance (NMR) structures of monomeric tail tube proteins (TTPs), and for phages T5 7 and λ 8 by fitting structures of monomeric TTPs 9 into a 6 Å cryo-EM density map. In 2020, a cryo-EM model of the baseplate of the Staphylococcus aureus 80α phage was reported, which includes two rings of the tail tube that are anchored within the baseplate and are, thus, not part of the flexible tube region 10 . Also, cryo-EM models of the tails of the flagellotropic tailed bacteriophage YSD1 11 and the Siphoviridae-like gene transfer agent of Rhodobacter capsulatus 12 were reported recently.…”

“…The tube-forming proteins share a common fold composed of two orthogonally packed β-sheets that hexamerize through the formation of an inner β-barrel that defines the lumen of the tube. However, variable elements such as loops, N-arms and C-arms are critical to mediate intermonomer contacts driving tube assembly in these systems, and sparse high resolution data are available on the position of these elements within the long-tailed phage tubes [6][7][8][9][10][11][12] .…”

Structural Insights into Lactococcal Siphophage p2 Baseplate Activation Mechanism

“…( B ) Same views as in A with the model of the second Dit hexamer (Dit-2) fitted in the map (surface representation). Four hexameric rings of the staphylococcal phage 80α major tail proteins (MTPs) are also shown in the tail as model structures for p2 MTPs (PDB ID 6V8I) [ 20 ]. ( C ) Topological model of the Dit-1 and Dit-2 assembly highlighting the organization of their N-terminal domain, arm-hand extension and galectin domain.…”