The Pennsylvania Railroad (PRR) class T1 duplex-drive 4-4-4-4 steam locomotives, introduced in 1942 with two prototypes and later in 1945-1946 with 50 production examples, were the last steam locomotives built for the PRR and arguably its most controversial.

The Pennsylvania Railroad (PRR) Class T1 duplex-drive 4-4-4-4 steam locomotives, introduced in 1942 with two prototypes and later in 1945-1946 with 50 production examples, were the last steam locomotives built for the PRR and arguably its most controversial.

Nov 17, 2020 · PRR T1 4-4-4-4 No. 5507 clatters through 21st Street interlocking in Chicago with the Broadway Limited for New York. A T1 on the Broadway is relatively rare, as dieselization of PRR’s top trains came soon after the giant duplexes arrived.

Jun 20, 2020 · PRR envisioned using the engines to haul express passenger trains on the 713-mile (1,147-km) route between Harrisburg, Pennsylvania and Chicago, Illinois. PRR anticipated that the T1 would replace its aging fleet of K4 engines.

The optional Escherichia coli prr locus restricts phage T4 mutants lacking polynucleotide kinase or RNA ligase. Underlying this restriction is the specific manifestation of the T4-induced anticodon nuclease, an enzyme which triggers the cleavage-ligation of the host tRNALys.

Jun 23, 1995 · Stp, a short polypeptide encoded by phage T4, has been implicated with activation of the anticodon nuclease. Here we confirm this notion and also demonstrate a second function of Stp: inhibition of EcoprrI restriction.

Bacteriophage T4 anticodon nuclease, polynucleotide kinase and RNA ligase reprocess the host lysine tRNA. Host tRNAs cleaved near the anticodon occur specifically in T4‐infected Escherichia coli prr strains which restrict polynucleotide kinase (pnk) or RNA ligase (rli) phage mutants.

Apr 1, 1994 · The prr locus was originally described as coding a ribonuclease that is activated after phage T4 infection to cut within the anticodon of a specific tRNA, inactivating protein synthesis and thus blocking phage development.

Feb 1, 2000 · A phage T4 inhibitor of DNA restriction activates anticodon nuclease, but other T4 proteins restore tRNA Lys. Detection of a homologous system in Neisseria and a different anticodon nuclease in colicin E5 suggest ubiquity and diversity of such tRNA toxins.

Presumably, lysine tRNA depletion, in the absence of polynucleotide kinase and RNA ligase mediated repair, underlies prr restriction. However, the nuclease, kinase and ligase may benefit T4 directly, by adapting levels or decoding specificities of host tRNAs to T4 codon usage.