AFM study of Escherichia coli RNA polymerase σ 70 subunit aggregation

Abstract

The self-assembly of Escherichia coli RNA polymerase σ 70 subunit was investigated using several experimental approaches. A novel rodlike shape was reported for σ 70 subunit aggregates. Atomic force microscopy reveals that these aggregates, or σ 70 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 σ 70 subunit may be an interesting object for investigation of amyloidosis as well as for biotechnological applications that exploit self-assembled bionanostructures. Polymerization of σ 70 subunit may be a competitive process with its three-dimensional crystallization and association with core RNA polymerase. From the Clinical Editor In this basic science study, the self-assembly of Escherichia coli RNA polymerase σ 70 subunit was investigated using atomic force microscopy and other complementary approaches.