7 Stress-70 Proteins and Their Interaction with Nucleotides

Abstract

I. INTRODUCTION
The first members of the 70-kD heat shock protein family, alias “stress-70” family, were identified in the 1970s. In 1974, Tissières and colleagues observed that the level of synthesis of some Drosophila cell proteins was dramatically enhanced by heat shock (Tissières et al. 1974). In addition, studies during the 1970s on bacteriophage λ yielded an Escherichia coli mutant that failed to support λ replication and was temperature-sensitive for growth at 42°C (Georgopoulos 1977). The product of the mutant gene was identified as the DnaK protein; the mutant became known as dnaK756 (Georgopoulos et al. 1979).

In 1984, sequencing of the E. coli DnaK protein revealed that it is homologous to the previously sequenced Drosophila 70-kD heat shock protein (Ingolia et al. 1980; Bardwell and Craig 1984). The high degree of sequence conservation of stress-70 genes within eukaryotes allowed the Drosophila gene to be used as a hybridization probe in cloning cDNAs of other stress-70 proteins (see, e.g., Hunt and Morimoto 1985; Voellmy et al. 1985; Wu et al. 1985; Munro and Pelham 1986). Purification of stress-70 proteins, including those that were present at low levels in cells, became relatively facile once it was recognized that they bound ATP tightly and could be affinity-purified on ATP-agarose (Welch and Feramisco 1985). As the number of sequences and purified proteins grew, it became apparent that many members of this family of proteins are present in cells under normal conditions; their presence is not strictly stress-related (for review, see Pelham 1986; Gething...