[Mycoplasma heat shock proteins and their genes]

Mycoplasmas (class Mollicutes) are the most simply organized prokaryotic organisms capable to self-reproduction. They are considered as a model of "minimal" cell. Systems preserved by mycoplasmas in their reductive evolution may play a fundamental role in viability of any cell. Information on the genes encoding heat shock proteins (HSP) in completely sequenced mycoplasma genomes was summarized and systematized. An attempt was made to explain the presence or absence in mycoplasmas of important bacterial chaperones and proteases. These HSP are necessary not only for cell stress resistance, but for protein homeostasis under normal conditions. The mechanisms of regulation of transcription of corresponding genes are considered. Properties and functions of the most completely characterized mycoplasmal HSP are discussed: DnaK, DnaJ-like, GroEL/GroES, ClpB, and small heat shock proteins (sHSP).