Abstract
In contrast with E. coli, cyanobacterial genomes generally contain two groEL homologues. Only groEL1 is arranged as an operon with groES like the E. coli groESL operon. The groEL2 sequences in cyanobacteria are much more evolutionarily diversified than the other ones. In chloroplasts of higher plants, two different forms of GroEL or Cpn60 also occur. It is not known why two GroELs are necessary. We hypothesize that GroEL2 plays a role under stress conditions, while GroEL1 plays a house-keeping role. In this presentation, we will show some evidence for specialized functions in the two GroELs in cyanobacteria. We will also show that the two GroELs have distinct in vitro properties that may provide structural basis for the functional specialization.
