Crystal structure of Escherichia coli phage HK620 tailspike: podoviral tailspike endoglycosidase modules are evolutionarily related

Abstract

SummaryBacteriophage HK620 infects Escherichia coli H and is closely related to Shigella phage Sf6 and Salmonella phage P22. All three Podoviridae recognize and cleave their respective host cell receptor polysaccharide by homotrimeric tailspike proteins. The three proteins exhibit high sequence identity in the 110 residues of their N-terminal particle-binding domains, but no apparent sequence similarity in their major, receptor-binding parts. We have biochemically characterized the receptor-binding part of HK620 tailspike and determined its crystal structure to 1.38 Å resolution. Its major domain is a right-handed parallel b-helix, as in Sf6 and P22 tailspikes. HK620 tailspike has endo-N-acetylglucosaminidase activity and produces hexasaccharides of an O18A1-type O-antigen. As indicated by the structure of a hexasaccharide complex determined at 1.6 Å resolution, the endoglycosidase-active sites are located intramolecularly, as in P22, and not between subunits, as in Sf6 tailspike. In contrast, the extreme C-terminal domain of HK620 tailspike forms a b-sandwich, as in Sf6 and unlike P22 tailspike. Despite the different folds, structure-based sequence alignments of the C-termini reveal motifs conserved between the three proteins. We propose that the tailspike genes of P22, Sf6 and HK620 have a common precursor and are not mosaics of unrelated gene fragments.

Crystal structure of an intramolecular chaperone mediating triple–β-helix folding

“…However, aside from their globular shape, the C-terminal extensions share no further structural similarity with the reported CIMCDs. The parallel-β-helix tailspike proteins (TSP) of the Podoviridae bacteriophages P22, Phi29, HK620, and Sf6 all contain a C-terminal trimerization domain that predominantly consists of β-strands, unlike the CIMCDs, which are mainly α-helical [19][20][21][22][23] . In the extensively studied P22 TSP, a combination of a triple β-helix, a β-prism and an antiparallel β-sheet interact in order to form a trimerization domain 21,22 .…”

“…β-sandwich has been found; however, it is unknown whether these domains are responsible for the assembly of the parallel β-helix 19,20 .…”

A Common Evolutionary Origin for Tailed-Bacteriophage Functional Modules and Bacterial Machineries

“…on May 12, 2018 by guest http://mmbr.asm.org/ conservation, also observed for tail fibers of members of the Siphoviridae, Podoviridae, and Myoviridae infecting Gram-negative hosts, highlights that the part of the tail adsorption protein that contacts the host is under heavy evolutionary pressure to diversify as they are presented to a genetically changing target in the host cell population (6,30). Hence, it appears that due to high selective pressure, tail fiber genes evolve more rapidly than other phage genes and that exchanges occur via horizontal transfer among phages crossing host phylogenetic boundaries (31).…”

Bacteriophage Tailspikes and Bacterial O-Antigens as a Model System to Study Weak-Affinity Protein–Polysaccharide Interactions

“…12 TSP attain specificity via long and shallow binding grooves, and several complexes of TSP with oligosaccharide fragments up to nonamer length have been described. 13,14,15 The…”