Fnctional analysis of the DnaK3, one of the essential molecular chaperones, in the cyanobacuterium Synechococcus elongatus PCC 7942.

Abstract

The Synechococcus elongatus PCC 7942 strain carrying a missense mutation in the peptide-binding domain of DnaK3, one of the essential dnaK gene products, exhibited temperature-sensitive growth. We also isolated suppressor mutants from this strain. One of the suppressors was mapped in the ribosomal protein gene rpl24 (synpcc7942_2221), which encodes the 50S ribosomal protein L24. Subcellular localization of three DnaK proteins was determined, and the results indicated that a amount of DnaK3 was dislocated from membrane-bound polysomes at non-permissive temperature in the dnaK3 temperature-sensitive mutant, whereas, in the suppressor mutant, the normal pattern of DnaK3 was restored. Possible roles of the DnaK3 protein, involving the translational control in the thylakoid membrane-bound polysomes, will be discussed.