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Three-dimensional reconstructions of the bacteriophage CUS-3 virion reveal a conserved coat protein I-domain but a distinct tailspike receptor-binding domain.

ABSTRACT: CUS-3 is a short-tailed, dsDNA bacteriophage that infects serotype K1 Escherichia coli. We report icosahedrally averaged and asymmetric, three-dimensional, cryo-electron microscopic reconstructions of the CUS-3 virion. Its coat protein structure adopts the "HK97-fold" shared by other tailed phages and is quite similar to that in phages P22 and Sf6 despite only weak amino acid sequence similarity. In addition, these coat proteins share a unique extra external domain ("I-domain"), suggesting that the group of P22-like phages has evolved over a very long time period without acquiring a new coat protein gene from another phage group. On the other hand, the morphology of the CUS-3 tailspike differs significantly from that of P22 or Sf6, but is similar to the tailspike of phage K1F, a member of the extremely distantly related T7 group of phages. We conclude that CUS-3 obtained its tailspike gene from a distantly related phage quite recently.

SUBMITTER: Parent KN

PROVIDER: S-EPMC4157081 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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Three-dimensional reconstructions of the bacteriophage CUS-3 virion reveal a conserved coat protein I-domain but a distinct tailspike receptor-binding domain.

Parent Kristin N KN Tang Jinghua J Cardone Giovanni G Gilcrease Eddie B EB Janssen Mandy E ME Olson Norman H NH Casjens Sherwood R SR Baker Timothy S TS

Virology 20140718

CUS-3 is a short-tailed, dsDNA bacteriophage that infects serotype K1 Escherichia coli. We report icosahedrally averaged and asymmetric, three-dimensional, cryo-electron microscopic reconstructions of the CUS-3 virion. Its coat protein structure adopts the "HK97-fold" shared by other tailed phages and is quite similar to that in phages P22 and Sf6 despite only weak amino acid sequence similarity. In addition, these coat proteins share a unique extra external domain ("I-domain"), suggesting that ...[more]

PMID: 25043589

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Project description:Myelination of the central nervous system (CNS) is critical to vertebrate nervous systems for efficient neural signaling. CNS myelination occurs as oligodendrocytes terminally differentiate, a process regulated in part by the myelin regulatory factor, MYRF. Using bioinformatics and extensive biochemical and functional assays, we find that MYRF is generated as an integral membrane protein that must be processed to release its transcription factor domain from the membrane. In contrast to most membrane-bound transcription factors, MYRF proteolysis seems constitutive and independent of cell- and tissue-type, as we demonstrate by reconstitution in E. coli and yeast. The apparent absence of physiological cues raises the question as to how and why MYRF is processed. By using computational methods capable of recognizing extremely divergent sequence homology, we identified a MYRF protein domain distantly related to bacteriophage tailspike proteins. Although occurring in otherwise unrelated proteins, the phage domains are known to chaperone the tailspike proteins' trimerization and auto-cleavage, raising the hypothesis that the MYRF domain might contribute to a novel activation method for a membrane-bound transcription factor. We find that the MYRF domain indeed serves as an intramolecular chaperone that facilitates MYRF trimerization and proteolysis. Functional assays confirm that the chaperone domain-mediated auto-proteolysis is essential both for MYRF's transcriptional activity and its ability to promote oligodendrocyte maturation. This work thus reveals a previously unknown key step in CNS myelination. These data also reconcile conflicting observations of this protein family, different members of which have been identified as transmembrane or nuclear proteins. Finally, our data illustrate a remarkable evolutionary repurposing between bacteriophages and eukaryotes, with a chaperone domain capable of catalyzing trimerization-dependent auto-proteolysis in two entirely distinct protein and cellular contexts, in one case participating in bacteriophage tailspike maturation and in the other activating a key transcription factor for CNS myelination.

Dataset Information

Three-dimensional reconstructions of the bacteriophage CUS-3 virion reveal a conserved coat protein I-domain but a distinct tailspike receptor-binding domain.

Publications

Three-dimensional reconstructions of the bacteriophage CUS-3 virion reveal a conserved coat protein I-domain but a distinct tailspike receptor-binding domain.

Similar Datasets

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