Inclusion Body Formation in E. coli Observed by Electron Microscopy

Scott Betts

Electron micrographs of tailspike and pectate lyase C inclusion bodies.

Two EM images of E. coli with inclusion bodies


During synthesis at 37°C, tailspike polypeptides containing temperature-sensitive folding mutations aggregate quantitatively in the cytoplasm of host E. coli cells. The aggregated polypeptide chains accumulate as electron-dense inclusion bodies visible at one or both poles of the cells in these electron micrographs.


The right-handed parallel ß-coil motif was discoverd in 1993 when the crystal structure of pectate lyase C was solved (Yoder MD, Keen NT, Jurnak F (1993) Science 260:1503-1507). This enzyme is a virulence factor secreted by Erwinia chrysanthemi, a soft-rot plant pathogen. In E. coli, recombinant pectate lyase C is targeted to the periplasmic space by its native signal peptide, where at low temperature it accumulates in the processed, mature form. At 37°C, however, pectate lyase C aggregates and accumulates as electron-dense inclusion bodies that appear to be excluded from the cytoplasm. The location of pectate lyase C inclusion bodies at the cell periphery suggests that they form in the periplasmic space.

Sample processing and electron microscopy were performed by Patricia Reilly at the Biomedical Electron Microscopy facility at MIT. The plasmid encoding the pectate lyase C precursor was kindly provided by Noel Keen and Frances Jurnak.

Related Publications:

Betts, SD & King, J (1998) Cold rescue of the thermolabile tailspike intermediate at the junction between productive folding and off-pathway aggregation. Protein Science 7(7):1516-1523. (Go to the article)

Betts S, Haase-Pettingell C, King J (1998) Mutational effects on inclusion body formation. Advances in Protein Chemistry 50:243-264.

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