title: Bacteriophage P22 tail accessory factor GP26 is a long triple-stranded coiled-coil.
abstract: P22 is a well characterized tailed bacteriophage that infects Salmonella enterica serovar Typhimurium. It is characterized by a "short" tail, which is formed by five proteins: the dodecameric portal protein (gp1), three tail accessory factors (gp4, gp10, gp26), and six trimeric copies of the tail-spike protein (gp9). We have isolated the gene encoding tail accessory factor gp26, which is responsible for stabilization of viral DNA within the mature phage, and using a variety of biochemical and biophysical techniques we show that gp26 is very likely a triple stranded coiled-coil protein. Electron microscopic examination of purified gp26 indicates that the protein adopts a rod-like structure approximately 210 angstroms in length. This trimeric rod displays an exceedingly high intrinsic thermostability (T(m) approximately 85 degrees C), which suggests a potentially important structural role within the phage tail apparatus. We propose that gp26 forms the thin needle-like fiber emanating from the base of the P22 neck that has been observed by electron microscopy of negatively stained P22 virions. By analogy with viral trimeric coiled-coil class I membrane fusion proteins, gp26 may represent the membrane-penetrating device used by the phage to pierce the host outer membrane.
authors.affiliation: Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13078, USA.
authors.forename: Dewan
authors.initials: D
authors.lastname: Andrews
authors.forename: James S
authors.initials: JS
authors.lastname: Butler
authors.forename: Jawdat
authors.initials: J
authors.lastname: Al-Bassam
authors.forename: Lisa
authors.initials: L
authors.lastname: Joss
authors.forename: Danella A
authors.initials: DA
authors.lastname: Winn-Stapley
authors.forename: Sherwood
authors.initials: S
authors.lastname: Casjens
authors.forename: Gino
authors.initials: G
authors.lastname: Cingolani
mesh_terms: D000595:Amino Acid Sequence; D017100:Bacteriophage P22 / Q000737:chemistry* / Q000648:ultrastructure; D019295:Computational Biology; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure; D017376:Viral Tail Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure
chemical_list: D011994:Recombinant Proteins; D017376:Viral Tail Proteins