10 Heat Shock Proteins in Hyperthermophiles

Publisher Summary This chapter describes a selection of experimental methods used to characterize heat shock proteins, starting with the identification of the heat shock regulons. It is suggested that their small genome size, coupled with the necessity to carry out ongoing protein salvage processes in the cell during normal growth, has resulted in minimal but highly efficient protein folding machinery in hyperthermophiles. Some proteins, such as AAA+ATPase of unknown function, are part of the heat shock response. In addition, a homolog of the Nascent Associated Complex has recently been described in the Archaea, although it is not clear how it relates to protein folding. Chaperone functions can be difficult to study in mesophiles, due to the multiplicity of chaperone encoding genes and parallel functions that they carry out. Heat shock regulation and chaperone functions in hyperthermophiles provide fresh insights into basic protein-folding mechanisms. The study of heat shock proteins involves decision-making as to which proteins are regulated by heat stress, the mechanisms of heat shock regulation, and the assignment of functions to the heat shock proteins by biophysical and biochemical approaches. The determination of chaperone functions is a very significant challenge, involving recombinant expression and characterization of individual HSPs, and elucidation of the functional roles of HSPs and their cooperative interactions with target proteins.