Extraction of an actin-like protein from the prokaryote Mycoplasma pneumoniae

Abstract

An actin-like protein has been identified in cell extracts from the prokaryote M. pneumoniae. This protein bears a striking resemblance to actin from vertebrates: the solubility of the protein during isolation is analogous to that of actin bound to myosin (soluble in high ionic strength salt solution and insoluble at low ionic strength), sodium dodecyl sulfate treatment of the partially purified M. pneumoniae extract produces a protein with an electrophoretic mobility very close to that of vertebrate actin in sodium dodecyl sulfate/polyacrylamide gels, treatment of preparations with ATP-Mg2+ allows separation of long curvilinear filaments, 5-6 nm wide, that closely resemble eukaryotic filamentous actin, and the prokaryotic filamentous actin binds vertebrate heavy meromyosin fragments to form hybrid complexes with the characteristic shape of periodic repeating arrowheads, and no heavy meromyosin is bound in the presence of ATP.