Bacteriophage P22 tail accessory factor GP26 is a long triple-stranded coiled-coil.
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.
Andrews
Dewan
D
Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13078, USA.
Butler
James S
JS
Al-Bassam
Jawdat
J
Joss
Lisa
L
Winn-Stapley
Danella A
DA
Casjens
Sherwood
S
Cingolani
Gino
G
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
D011994:Recombinant Proteins; D017376:Viral Tail Proteins