AFM study of Escherichia coli RNA polymerase σ70 subunit aggregation

The self-assembly of Escherichia coli RNA polymerase σ70 subunit was investigated using several experimental approaches. A novel rodlike shape was reported for σ70 subunit aggregates. Atomic force microscopy reveals that these aggregates, or σ70 polymers, have a straight rodlike shape 5.4 nm in diameter and up to 300 nm in length. Atomic force microscopy data, Congo red binding assay, and sodium dodecyl sulfate gel electrophoresis confirm the amyloid nature of observed aggregates. The process of formation of rodlike structures proceeds spontaneously under nearly physiological conditions. E. coli RNA polymerase σ70 subunit may be an interesting object for investigation of amyloidosis as well as for biotechnological applications that exploit self-assembled bionanostructures. Polymerization of σ70 subunit may be a competitive process with its three-dimensional crystallization and association with core RNA polymerase.From the Clinical EditorIn this basic science study, the self-assembly of Escherichia coli RNA polymerase σ70 subunit was investigated using atomic force microscopy and other complementary approaches.

Graphical AbstractE. coli RNA polymerase σ70 subunit spontaneously aggregates under nearly physiological conditions into rodlike fibrils of amyloid nature. The figure depicts an AFM image of σ70 subunit rodlike aggregates and their dimensions.Figure optionsDownload high-quality image (230 K)Download as PowerPoint slide