The tail sheath structure of bacteriophage T4: a molecular machine for infecting bacteria (original) (raw)
Related papers
J Mol Biol, 2009
Bacteriophages of the Podoviridae family use short non-contractile tails to inject their genetic material into Gram-negative bacteria. In phage P22, the tail contains a thin needle, encoded by the phage gene 26, which is essential both for stabilization and ejection of the packaged viral genome. Bio-informatic analysis of the N-terminal domain of gp26 (residues 1-60) led us to identify a family of genes encoding putative homologues of the tail needle gp26. To validate this idea experimentally and to explore their diversity, we cloned the gp26-like gene from phages HK620, Sf6, HS1, and characterized these gene products in solution. All gp26-like factors contain an elongated α-helical coiled-coil core consisting of repeating, adjacent trimerization heptads and form trimeric fibers with length ranging between about 240Å to 300Å. Gp26-tail needles display high structural stability in solution, with T m (temperature of melting) between 85-95°C. To determine how the structural stability of these phage fibers correlates with the length of the α-helical core, we investigated the effect of insertions and deletions in the helical core. In P22 tail needle, we identified an 85-residue long helical domain, termed MiCRU (Minimal Coiled-coil Repeat Unit), that can be inserted in frame inside gp26 helical core, preserving the straight morphology of the fiber. Likewise, we were able to remove three quarters of the helical core of HS1 tail needle minimally decreasing the stability of the fiber. We conclude that in the gp26 family of tail needles, structural stability increases nonlinearly with the length of the α-helical core. Thus, the overall stability of these bacteriophage fibers is not solely dependent on the number of trimerization repeats in the α-helical core.
Journal of Molecular Biology, 2009
Bacteriophages of the Podoviridae family use short non-contractile tails to inject their genetic material into Gram-negative bacteria. In phage P22, the tail contains a thin needle, encoded by the phage gene 26, which is essential both for stabilization and ejection of the packaged viral genome. Bio-informatic analysis of the N-terminal domain of gp26 (residues 1-60) led us to identify a family of genes encoding putative homologues of the tail needle gp26. To validate this idea experimentally and to explore their diversity, we cloned the gp26-like gene from phages HK620, Sf6, HS1, and characterized these gene products in solution. All gp26-like factors contain an elongated α-helical coiled-coil core consisting of repeating, adjacent trimerization heptads and form trimeric fibers with length ranging between about 240Å to 300Å. Gp26-tail needles display high structural stability in solution, with T m (temperature of melting) between 85-95°C. To determine how the structural stability of these phage fibers correlates with the length of the α-helical core, we investigated the effect of insertions and deletions in the helical core. In P22 tail needle, we identified an 85-residue long helical domain, termed MiCRU (Minimal Coiled-coil Repeat Unit), that can be inserted in frame inside gp26 helical core, preserving the straight morphology of the fiber. Likewise, we were able to remove three quarters of the helical core of HS1 tail needle minimally decreasing the stability of the fiber. We conclude that in the gp26 family of tail needles, structural stability increases nonlinearly with the length of the α-helical core. Thus, the overall stability of these bacteriophage fibers is not solely dependent on the number of trimerization repeats in the α-helical core.
Structural Studies of the Phage G Tail Demonstrate an Atypical Tail Contraction
Viruses, 2021
Phage G is recognized as having a remarkably large genome and capsid size among isolated, propagated phages. Negative stain electron microscopy of the host–phage G interaction reveals tail sheaths that are contracted towards the distal tip and decoupled from the head–neck region. This is different from the typical myophage tail contraction, where the sheath contracts upward, while being linked to the head–neck region. Our cryo-EM structures of the non-contracted and contracted tail sheath show that: (1) The protein fold of the sheath protein is very similar to its counterpart in smaller, contractile phages such as T4 and phi812; (2) Phage G’s sheath structure in the non-contracted and contracted states are similar to phage T4’s sheath structure. Similarity to other myophages is confirmed by a comparison-based study of the tail sheath’s helical symmetry, the sheath protein’s evolutionary timetree, and the organization of genes involved in tail morphogenesis. Atypical phase G tail con...
The Molecular Architecture of the Bacteriophage T4 Neck
Journal of Molecular Biology, 2013
A hexamer of the bacteriophage T4 tail terminator protein, gp15, attaches to the top of the phage tail stabilizing the contractile sheath and forming the interface for binding of the independently assembled head. Here we report the crystal structure of the gp15 hexamer, describe its interactions in T4 virions that have either an extended tail or a contracted tail, and discuss its structural relationship to other phage proteins. The neck of T4 virions is decorated by the "collar" and "whiskers", made of fibritin molecules. Fibritin acts as a chaperone helping to attach the long tail fibers to the virus during the assembly process. The collar and whiskers are environment-sensing devices, regulating the retraction of the long tail fibers under unfavorable conditions, thus preventing infection. Cryo-electron microscopy analysis suggests that twelve fibritin molecules attach to the phage neck with six molecules forming the collar and six molecules forming the whiskers.
Mass distribution of a probable tail-length-determining protein in bacteriophage T4
Proceedings of the National Academy of Sciences, 1985
Analysis of dark-field scanning transmission electron micrographs of unstained freeze-dried specimens established that the interior of the intact bacteriophage T4 tail tube contains extra density that is missing in tubes artificially emptied by treatment with 3 M guanidine hydrochloride. The mass of the tail tube is 3.1 x 106 daltons, and the central channel is 3.2 nm in diameter. Quantitative analysis of the density data is consistent with the presence of up to six strands of a protein molecule in the central channel that could serve as the template or ruler structure that determines the length of the bacteriophage tail and that could be injected into the cell with the phage DNA.