9 Properties of the Heat Shock Proteins of Escherichia coli and the Autoregulation of the Heat Shock Response

Abstract

I. INTRODUCTION
The studies of bacteriophage λ/Escherichia coli interactions, initiated more than 25 years ago, have resulted in the identification of a plethora of interesting and useful host functions (for summary, see Friedman et al. 1984; Georgopoulos et al. 1990). These bacterial functions are essential not only for bacteriophage λ growth and development, but for bacterial growth as well. The ability to study both λ-specific and host-specific phenotypes at nonpermissive temperatures was instrumental in the elucidation of the function of these bacterial genes. In many instances, these genetic studies identified a series of E. coli genes that are required for a specific step in λ development, strongly suggesting that their gene products act synergistically to carry out the particular λ developmental step. The availability of these genes on plasmids plus the large number of mutations in them was the starting block for the elucidation of the molecular mechanism of the action of their gene products.

The best studied of these E. coli functions, namely, the NusA/NusB transcriptional antitermination system and the DnaK and GroEL chaperones, all turned out to be supramolecular machines made up of intimately interacting parts (Friedman et al. 1984; Das 1992; Georgopoulos 1992; Georgopoulos and Welch 1993). For the purpose of this particular volume, the most interesting E. coli functions are the DnaK chaperone machine, composed of the DnaK (the hsp70 homolog), DnaJ (the hsp40 homolog), and GrpE heat shock proteins, and the GroEL chaperone machine, composed of the GroES (the hsp10 homolog) and GroEL (the hsp60...