Regulation and organization of the groE and dnaK operons in Eubacteria.

groEL and dnaK are the most highly conserved protein-coding genes known. Most groEL operons and several dnaK and dnaJ operons contain a highly conserved inverted repeat (IR) sequence in their regulatory region. So far, this IR has been found only as part of the groE, dnaK and dnaJ operons and genes. In most cases, the IR is part of the operon transcript, and is involved in the regulation of expression at both the DNA and mRNA levels. A detailed analysis of groE and dnaK operons indicates that the organization of the groE operons is highly conserved. They contain only the groES and groEL genes and always in the same order. In contrast, the organization of the dnaK operons has changed during evolution: genes have been added and deleted from it, and the gene order within the operon is variable.