Localization of functional polypeptides in bacterial inclusion bodies

Appl Environ Microbiol. 2007 Jan;73(1):289-94. doi: 10.1128/AEM.01952-06. Epub 2006 Nov 3.

Abstract

Bacterial inclusion bodies, while showing intriguing amyloid-like features, such as a beta-sheet-based intermolecular organization, binding to amyloid-tropic dyes, and origin in a sequence-selective deposition process, hold an important amount of native-like secondary structure and significant amounts of functional polypeptides. The aggregation mechanics supporting the occurrence of both misfolded and properly folded protein is controversial. Single polypeptide chains might contain both misfolded stretches driving aggregation and properly folded protein domains that, if embracing the active site, would account for the biological activities displayed by inclusion bodies. Alternatively, soluble, functional polypeptides could be surface adsorbed by interactions weaker than those driving the formation of the intermolecular beta-sheet architecture. To explore whether the fraction of properly folded active protein is a natural component or rather a mere contaminant of these aggregates, we have explored their localization by image analysis of inclusion bodies formed by green fluorescent protein. Since the fluorescence distribution is not homogeneous and the core of inclusion bodies is particularly rich in active protein forms, such protein species cannot be passively trapped components and their occurrence might be linked to the reconstruction dynamics steadily endured in vivo by such bacterial aggregates. Intriguingly, even functional protein species in inclusion bodies are not excluded from the interface with the solvent, probably because of the porous structure of these particular protein aggregates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Capsid Proteins / genetics
  • Capsid Proteins / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli / ultrastructure*
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Inclusion Bodies / metabolism*
  • Inclusion Bodies / ultrastructure*
  • Microscopy, Confocal
  • Nitrophenylgalactosides / metabolism
  • Peptides / genetics
  • Peptides / metabolism*
  • Protein Folding
  • Protein Structure, Secondary

Substances

  • Capsid Proteins
  • Peptides
  • VP1 protein, Foot-and-mouth disease virus
  • Green Fluorescent Proteins
  • 2-nitrophenylgalactoside
  • Nitrophenylgalactosides