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Structure. 2014 Apr 8;22(4):539-48. doi: 10.1016/j.str.2014.02.006. Epub 2014 Mar 13.

The structure and assembly mechanism of a novel three-stranded tubulin filament that centers phage DNA.

Author information

1
Department of Biochemistry and Biophysics and the Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA.
2
Division of Biological Sciences, University of California, San Diego, San Diego, CA 92093, USA.
3
Department of Biochemistry and Biophysics and the Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA. Electronic address: agard@msg.ucsf.edu.

Abstract

Tubulins are a universally conserved protein superfamily that carry out diverse biological roles by assembling filaments with very different architectures. The underlying basis of this structural diversity is poorly understood. Here, we determine a 7.1 Å cryo-electron microscopy reconstruction of the bacteriophage-encoded PhuZ filament and provide molecular-level insight into its cooperative assembly mechanism. The PhuZ family of tubulins is required to actively center the phage within infected host cells, facilitating efficient phage replication. Our reconstruction and derived model reveal the first example of a three-stranded tubulin filament. We show that the elongated C-terminal tail simultaneously stabilizes both longitudinal and lateral interactions, which in turn define filament architecture. Identified interaction surfaces are conserved within the PhuZ family, and their mutagenesis compromises polymerization in vitro and in vivo. Combining kinetic modeling of PhuZ filament assembly and structural data, we suggest a common filament structure and assembly mechanism for the PhuZ family of tubulins.

PMID:
24631461
PMCID:
PMC3999902
DOI:
10.1016/j.str.2014.02.006
[Indexed for MEDLINE]
Free PMC Article

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