The in vitro self-assembly of supramolecular structures after the spontaneous disassembly of carotovoricins

The self-assembly of supramolecular structures (empty sheaths and polysheaths of the macromolecular Erwinia carotovora bacteriocins) was studied by electron microscopy in the course of 1- to 2-year incubation of phage particles at 4degreesC. This study showed that the empty sheaths and polysheaths of the bacteriocins of eight E. carotovora strains spontaneously assemble at the self-assembly centers (or crystallization centers), which have a diameter of 26-65 nm and contain a dense proteinaceous material. The self-assembly center consists of two components, a primer and the structural protein of contracted sheaths. Empty sheaths assembled in the crystallization centers are polar structures synthesized through the stepwise head-to-tail polymerization of monomeric units. The supramolecular structures of two E. carotovora 62A bacteriocins are assembled in a different way. At the early stages of their self-assembly, a reticular structure is formed, which then transforms into very long polysheaths composed of monomers. Along with polysheaths, rounded or lamplike structures 33-117 nm in size composed of the subunits of contracted sheaths are produced. Carotovoricins may serve as suitable objects for the study of the self-assembly of elementary biological structures.