Mycoplasma heat shock proteins and their genes

Mycoplasmas (class Mollicutes) are the simplest prokaryotic organisms capable of independent reproduction and are therefore considered a natural model of a “minimal” cell. The systems retained by mycoplasmas in the course of their reductive evolution may be fundamental for all cells. This is the first review to summarize and systematize available information concerning the genes encoding the heat shock proteins (HSP) in mycoplasma. An attempt is made to analyze the presence or absence of the mycoplasma analogues of the major bacterial chaperones and proteases, which determine cell resistance to stresses, as well as protein homeostasis under optimal growth conditions. The data on the mechanisms for the regulation of transcription of the HSP genes in mycoplasma are presented. The properties and functions of the best-characterized mycoplasma HSP, namely, DnaK, DnaJ-like proteins, the GroEL/GroES system, ClpB, and small heat shock proteins (sHSP), are discussed.