Bacteriophage T5 tail tube structure suggests a trigger mechanism for Siphoviridae DNA ejection

Abstract

The vast majority of phages, bacterial viruses, possess a tail ensuring host recognition, cell wall perforation and safe viral DNA transfer from the capsid to the host cytoplasm. Long flexible tails are formed from the tail tube protein (TTP) polymerised as hexameric rings around and stacked along the tape measure protein (TMP). Here, we report the crystal structure of T5 TTP pb6 at 2.2 Å resolution. Pb6 is unusual in forming a trimeric ring, although structure analysis reveals homology with all classical TTPs and related tube proteins of bacterial puncturing devices (type VI secretion system and R-pyocin). Structures of T5 tail tubes before and after interaction with the host receptor were determined by cryo-electron microscopy at 6 Å resolution. Comparison of these two structures reveals that host-binding information is not propagated to the capsid through conformational changes in the tail tube, suggesting a role of the TMP in this information transduction process.

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

“…Other studies have revealed no apparent conformational change in the tail tube associated with the infection process in siphoviruses [32]. Even in the myoviruses, tail contraction itself is not the signal that leads to ejection [11,35]. Our observation of TMP α-helices associated with Tal resolves this conundrum: upon release by Tal, the TMP α-helices might act as a "pull cord" that drags the DNA along during injection ( Fig 6C).…”

“…This luminal β-sheet contains an extended insertion loop between β2 and β3 (the "stacking loop") that reaches across the �3 Å space that separates tail rings and inserts into a pocket between two subunits in the adjacent ring ( Fig 3A). The equivalent loop in the major tail proteins of phages λ, T5 and SPP1 was shown to play an essential role in tail polymerization [33][34][35].…”

“…No equivalent contact has been seen in other systems. The major tail proteins of phages λ, SPP1 and T5 instead have an additional C-terminal immunoglobulin (Ig)-like domain [33][34][35]. Overall, the tail tube domain of 80α MTP differs from those of λ gpV and SPP1 gp17.1 with Cα RMSD values of 4.2 Å and 5.6 Å, respectively, between the most well-matched residues (S1 Table,…”

Solid‐State NMR H–N–(C)–H and H–N–C–C 3D/4D Correlation Experiments for Resonance Assignment of Large Proteins

“…Experiments such as those presented herein will contribute to extending the applicabilityo fM AS ssNMRt op roteins of increasing size, complexity and biological interest. Regions with significant Dd valuesare highlighted in red, and plotted onto the structural model of the full-length pb6tubes [30] (panel C). ChemPhysChem 2017ChemPhysChem , 18,2697ChemPhysChem -2703 www.chemphyschem.org 2017 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim…”

“…Af irst observation is that the chemical shifts are, overall, very similar,e stablishing that this domain, as part of the assembled tube, retains its conformation. The regionsw ith significant differences in chemical shifts are plotted onto as tructural model of the pb6 tail tubes [30] in Figure6.T hese parts are located in close proximity to the remainder of the protein, that is, where the Ig-like domain contacts the core of the tail tube, as one expects from the structuralm odel.W ea re currently extending the assignmentso fp b6 to the remaining 374 residues,i no rder to characterize the structure, interactions and dynamics of these assemblies in detail. The approaches presented herein will be a key elementinp ursuing thesestudies.…”