Quantitative characterization of all single amino acid variants of a viral capsid-based drug delivery vehicle

Nat Commun. 2018 Apr 11;9(1):1385. doi: 10.1038/s41467-018-03783-y.

Abstract

Self-assembling proteins are critical to biological systems and industrial technologies, but predicting how mutations affect self-assembly remains a significant challenge. Here, we report a technique, termed SyMAPS (Systematic Mutation and Assembled Particle Selection), that can be used to characterize the assembly competency of all single amino acid variants of a self-assembling viral structural protein. SyMAPS studies on the MS2 bacteriophage coat protein revealed a high-resolution fitness landscape that challenges some conventional assumptions of protein engineering. An additional round of selection identified a previously unknown variant (CP[T71H]) that is stable at neutral pH but less tolerant to acidic conditions than the wild-type coat protein. The capsids formed by this variant could be more amenable to disassembly in late endosomes or early lysosomes-a feature that is advantageous for delivery applications. In addition to providing a mutability blueprint for virus-like particles, SyMAPS can be readily applied to other self-assembling proteins.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acids / chemistry*
  • Amino Acids / metabolism
  • Capsid / chemistry*
  • Capsid / metabolism
  • Capsid / ultrastructure
  • Capsid Proteins / chemistry*
  • Capsid Proteins / genetics
  • Capsid Proteins / metabolism
  • Endosomes / metabolism
  • Hydrogen-Ion Concentration
  • Hydrophobic and Hydrophilic Interactions
  • Levivirus / chemistry*
  • Levivirus / metabolism
  • Levivirus / ultrastructure
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Mutation*
  • Protein Engineering / methods
  • Protein Stability
  • Protein Structure, Secondary
  • Proteolysis
  • Static Electricity
  • Virion / chemistry*
  • Virion / metabolism
  • Virion / ultrastructure

Substances

  • Amino Acids
  • Capsid Proteins