The Tip of the Tail Needle Affects the Rate of DNA Delivery by Bacteriophage P22

Abstract

The P22-like bacteriophages have short tails. Their virions bind to their polysaccharide receptors through six trimeric tailspike proteins that surround the tail tip. These short tails also have a trimeric needle protein that extends beyond the tailspikes from the center of the tail tip, in a position that suggests that it should make first contact with the host’s outer membrane during the infection process. The base of the needle serves as a plug that keeps the DNA in the virion, but role of the needle during adsorption and DNA injection is not well understood. Among the P22-like phages are needle types with two completely different C-terminal distal tip domains. In the phage Sf6-type needle, unlike the other P22-type needle, the distal tip folds into a “knob” with a TNF-like fold, similar to the fiber knobs of bacteriophage PRD1 and Adenovirus. The phage HS1 knob is very similar to that of Sf6, and we report here its crystal structure which, like the Sf6 knob, contains three bound L-glutamate molecules. A chimeric P22 phage with a tail needle that contains the HS1 terminal knob efficiently infects the P22 host, Salmonella enterica, suggesting the knob does not confer host specificity. Likewise, mutations that should abrogate the binding of L-glutamate to the needle do not appear to affect virion function, but several different other genetic changes to the tip of the needle slow down potassium release from the host during infection. These findings suggest that the needle plays a role in phage P22 DNA delivery by controlling the kinetics of DNA ejection into the host.

Structural Plasticity of the Protein Plug That Traps Newly Packaged Genomes in Podoviridae Virions

“…However, entirely replacing the P22 C-terminal tip spanning residues 141-233 with the short (ϳ27 residues) foldon domain of bacteriophage T4 fibritin (32) reduces infectivity and slows potassium release from the host during infection. Together, these findings support the idea that the tail needle tip plays a direct role in DNA delivery, possibly by controlling the kinetics of DNA release (31).…”

“…Although the kinetics of DNA release in vitro is much slower than the physiological rate of phage genome ejection, the signal for tail needle release and genome injection is likely transmitted from the tailspike to the tail needle through a series of conformational changes within the tail hub. Swapping the gp26 C-terminal tip with the corresponding domain of the tail needle knob (17) of bacteriophage Sf6 provided compelling evidence that this moiety does not confer host specificity between Escherichia coli, Shigella flexneri, and Salmonella enterica, at least under laboratory conditions (31). However, entirely replacing the P22 C-terminal tip spanning residues 141-233 with the short (ϳ27 residues) foldon domain of bacteriophage T4 fibritin (32) reduces infectivity and slows potassium release from the host during infection.…”

Exploring the Balance between DNA Pressure and Capsid Stability in Herpesviruses and Phages

“…Procedures were performed as previously described for isolation of wild-type (wt) P22 (c1-7 13-amH101) (16) and virions containing wild-type (cI60) or truncated (b221) genome lengths (17). The His73Leu change in the P22 tail needle protein (gp26) was created by recombinantly replacing the His73 codon with CTC in the P22 prophage of Salmonella enterica strain UB-1790, as described previously (18,19). HSV-1 capsids containing wild-type (KOS strain) or truncated (recombinant R7023 F strain [20]) genomes were isolated as previously described (9).…”

Three-dimensional reconstructions of the bacteriophage CUS-3 virion reveal a conserved coat protein I-domain but a distinct tailspike receptor-binding domain

“…The obvious difference is the distal “knob” domain that is only present in Sf6. For the P22-like phages, this knob domain is highly conserved when present, and it is encoded by about 40% of the members of this group of phages whose genomes have been sequenced (Leavitt et al , 2013b). …”

“…Diversity of tailed phages is increased beyond simple linear divergence by means of the extensive horizontal exchange of genetic information, which produces “mosaic genomes” (see, for example Casjens et al , 1992; Hendrix, 2002; Casjens, 2005). The large P22-like phage group that includes these three coat protein subtypes has proven to be fertile ground for the examination of past horizontal exchanges of virion assembly genes (Casjens and Thuman-Commike, 2011; Leavitt et al , 2013a; Leavitt et al , 2013b). However, many questions remain about whether all phage genes are free to participate in random horizontal transfer or whether functionally-related sets of genes that encode interacting proteins co-evolve to a point where they can no longer be separated by such exchange events.…”