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Author Notes:

Vincent P. Conticello: vcontic@emory.edu

S.A.H. and V.P.C. designed research; S.A.H., F.W., S.W., M.A.B.K., A.O., J.S.W., X.Z., and E.H.E. performed research; S.A.H., F.W., S.W., M.A.B.K., T.O., J.S.W., X.Z., E.H.E., and V.P.C. analyzed data; and S.A.H., F.W., S.W., M.A.B.K., T.O., A.O., J.S.W., X.Z., E.H.E., and V.P.C. wrote the paper.

The authors declare no conflict of interest.

Subject:

Research Funding:

This research was, in part, supported by the National Cancer Institute’s National Cryo-EM Facility at the Frederick National Laboratory for Cancer Research under contract HSSN261200800001E.

This research used resources of the Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract DE-AC02-06CH11357.

This research used the National Cancer Institute’s National Cryo-EM Facility at the Frederick National Laboratory for Cancer Research.

The cryo-EM work on the HEAT_R1 filaments was conducted at the Molecular Electron Microscopy Core facility at the University of Virginia, which is supported by the School of Medicine and built with NIH grant G20-RR31199

The Titan Krios within that core was funded by NIH shared instrumentation (SIG) grant S10-RR025067; and the Falcon II direct detector was funded by NIH SIG S10-OD018149.

This work was supported by NSF Division of Material Research grant 1533958 (to V.P.C. and E.H.E.).

Keywords:

  • Science & Technology
  • Multidisciplinary Sciences
  • Science & Technology - Other Topics
  • tandem repeat proteins
  • cryo-EM
  • helical nanotube
  • self-assembly
  • REPEAT-PROTEIN
  • MICROSCOPY STRUCTURE
  • MOLECULAR-STRUCTURE
  • CRYSTAL-STRUCTURE
  • RATIONAL DESIGN
  • PILUS REVEALS
  • CRYO-EM
  • DNA
  • RECONSTRUCTION
  • INDUCTION

Ambidextrous helical nanotubes from self-assembly of designed helical hairpin motifs

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Journal Title:

Proceedings of the National Academy of Sciences

Volume:

Volume 116, Number 29

Publisher:

, Pages 14456-14464

Type of Work:

Article | Final Publisher PDF

Abstract:

Tandem repeat proteins exhibit native designability and represent potentially useful scaffolds for the construction of synthetic bio-mimetic assemblies. We have designed 2 synthetic peptides, HEAT_R1 and LRV_M3Δ1, based on the consensus sequences of single repeats of thermophilic HEAT (PBS_HEAT) and Leucine-Rich Variant (LRV) structural motifs, respectively. Self-assembly of the peptides afforded high-aspect ratio helical nanotubes. Cryo-electron microscopy with direct electron detection was employed to analyze the structures of the solvated filaments. The 3D reconstructions from the cryo-EM maps led to atomic models for the HEAT_R1 and LRV_M3Δ1 filaments at resolutions of 6.0 and 4.4 Å, respectively. Surprisingly, despite sequence similarity at the lateral packing interface, HEAT_R1 and LRV_M3Δ1 filaments adopt the opposite helical hand and differ significantly in helical geometry, while retaining a local conformation similar to previously characterized repeat proteins of the same class. The differences in the 2 filaments could be rationalized on the basis of differences in cohesive interactions at the lateral and axial interfaces. These structural data reinforce previous observations regarding the structural plasticity of helical protein assemblies and the need for high-resolution structural analysis. Despite these observations, the native designability of tandem repeat proteins offers the opportunity to engineer novel helical nanotubes. Moreover, the resultant nanotubes have independently addressable and chemically distinguishable interior and exterior surfaces that would facilitate applications in selective recognition, transport, and release.

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© 2019 National Academy of Sciences. All rights reserved.

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