The ΦO18P major capsid selleck inhibitor protein is similar to the capsid proteins of phages K139, ΦCTX, 186, and the Burkholderia phages. III. The Spounavirinae This proposed subfamily contains the ICTV-recognized genus “”SPO1-like viruses”" and, on the basis of our results, a proposed new genus (the “”Twort-like viruses”") and two peripherally related viruses, Lactobacillus plantarum phage LP65 [41] and Enterococcus faecalis phage φEF24C [42, 43]. All of these are virulent, broad-host range phages which infect members of the Firmicutes. They possess isometric heads of 87-94 nm in diameter and conspicuous capsomers, striated 140-219
nm long tails, a double base plate, and globular structures at the tail tip. The latter have been resolved as base plate spikes and short kinked tail fibers with six-fold symmetry [44]. Members of this group usually possess large (127-142 kb) nonpermuted genomes with 3.1-20 kb terminal redundancies [45, 46]. The proposed name for this subfamily is derived from SPO plus una (latin
learn more for “”one”"). While the head diameter of Bacillus phage SPO1, of 87 nm [47], is consistent with membership in the group, its tail is significantly shorter than that of most members (140-150 nm) [3, 48], and, the DNA contains 5-hydroxymethyluracil (HMU) rather than thymine. The outliers of this group comprise phages LP65 [41] and φEF24C [42, 43]. At 193 nm, the tail of phage LP65 is similar in length to that of other members of this group, but its genome is not terminally redundant [41]. Lastly, the genome size (142 kb), proteome and morphology of Enterococcus phage φEF24C is clearly consistent with membership in this group (head diameter 93 nm; tail length 204 nm), but its genome is circularly permuted. Their close relationship was discussed in a recent
paper [44]. Using a BLASTP raw threshold score Reverse transcriptase of 100 and CoreGenes 3.0 http://binf.gmu.edu:8080/CoreGenes3.0/ to compare the proteomes of Twort, A511, LP65, and φEF24C against SPO1, we identified two clusters of genes which are conserved. These corresponded to packaging and morphogenesis genes (SPO1 gp2.11 to gp16.2); and the cluster of replication genes, including helicase, exonuclease, primase, and resolvase (SPO1 gp19.5 – gp24.1). The DNA polymerases (SPO1 gp31 and homologs) of these phages are related more closely to bacterial-type I DNA polymerases than other phage deoxynucleotide polymerizing enzymes. The presence of this website host-related proteins in viruses has been observed by Dinsdale et al. [49] and elegantly explained by Serwer [50]. Metagenomic studies by the former group indicate the presence of numerous host-related proteins, including those related to motility and chemotaxis, in the virome fractions.